Week 6

Question 1

Zygote

Answer 1

The cell formed by the fusion of two gametes

Question 2

Morula

Answer 2

More than 32 cells, undifferentiated, still in ball form

Question 3

Where do the first few cell divisions occur?

Answer 3

In the oviduct

Question 4

What is the significance of the inner and outer cells in the morula?

Answer 4

Inner cells form the embryo, outer cells form the placenta

Question 5

What is compaction?

Answer 5

Tight junctions and gap junctions form between adjacent blastomeres, and the cells flatten together to form a tight ball in a process called compaction. Cadherins appear to play important roles in compaction, because interfering with cadherins prevents this process. During compaction, the cells also become polarized, with a well- defined apical and basal surface. A fluid-filled space, the blastocoel, appears in the embryo, which is now called a blastocyst.

Question 6

When and where does implantation usually occur?

What happens to the zona pellucida prior to implantation?

Answer 6

At 6 to 7 days after fertilization, the blastocyst reaches the uterus and implants. Before the embryo can attach to the uterine epithelium, however, it must get rid of the zona pellucida, which still envelopes the embryo. Hydrolytic enzymes are released by the embryo that degrade the wall of the zona, allowing the blastocyst to squeeze out, or “hatch” out of the zona. It is thought that the presence of the zona prior to hatching helps prevent ectopic implantation.

Question 7

What is placenta previa?



Answer 7

Implantation close to the mouth of the cervix results in the placenta partially covering the cervical canal, a condition known as placenta previa. Placenta previa can cause hemorrhage during pregnancy and can threaten the survival of the fetus and mother.

Question 8

How does the bilaminar disc form?

Answer 8

On about day 7 after fertilization, at about the time of implantation, a number of changes occur at the animal pole (the inner cell mass) of the embryo. A fluid space appears between the inner cell mass and the adjacent trophectoderm cells; this space will become the amniotic cavity. This process, called delamination, isolates the inner cell mass as a separate entity from the trophoblast. The inner cell mass flattens and forms a roughly circular disc, composed of two layers of cells. The cells closest to the forming amniotic cavity are tall columnar cells, and collectively are called the epiblast. The underlying cells are more cuboidal and form the hypoblast. The epiblast will eventually give rise to the embryo, as well as some extraembryonic structures, while the hypoblast will form extraembryonic structures only. The formation of epiblast and hypoblast is sometimes referred to as the delamination of the inner cell mass. The epiblast side of the disc identifies the dorsal direction. By about day 9, cells of the hypoblast have proliferated and extend below the embryonic disc to enclose a space called the primary yolk sac. A number of these cells break free from the wall of the primary yolk sac to fill the space between the yolk sac and the trophoblast and are subsequently called extraembryonic mesoderm cells. A dense cluster of extraembryonic mesoderm cells connect the bilaminar disc to the trophoblast; this connection will become the umbilical cord. Meanwhile, a distinct cellular layer, apparently derived from the cytotrophoblast, begins to form a roof (the amniotic membrane) over the amniotic cavity.

Question 9

What are the epiblast and hypoblast? From what layer does the embryo proper arise?

Answer 9

The cells closest to the forming amniotic cavity are tall columnar cells, and collectively are called the epiblast. The underlying cells are more cuboidal and form the hypoblast. The epiblast will eventually give rise to the embryo, as well as some extraembryonic structures, while the hypoblast will form extraembryonic structures only. The formation of epiblast and hypoblast is sometimes referred to as the delamination of the inner cell mass.

Question 10

When does gastrulation occur?

Answer 10

Gastrulation takes place after cleavage and the formation of the blastula and primitive streak.

Question 11

What is the primitive streak?

Answer 11

The first sign of gastrulation is a
migration of epiblast cells toward the midline of the
embryonic disc. The thickening formed is called the primitive streak, and serves to demarcate the anterior-postior and left-right axes of the embryo

Question 12

Primitive node (Hensen’s node)?

Answer 12

As epiblast cells continue migrating, the streak extends in a rostral direction along the disc, and a thickening - Hensen’s node (or the primitive node) - appears at the rostral end of the streak. Then, the streak turns into a groove, through which other epiblast cells migrate.

Question 13

What three germ layers arise from the process of gastrulation?

Answer 13

Epiblast cells migrate ventrally through the primitive streak to give rise to mesoderm and endoderm. The ventrally-most migrating cells displace hypoblast cells and form embryonic endoderm. Cells that come to reside between the epiblast and endoderm become mesoderm. The cells remaining in the epiblast become ectoderm.

Question 14

What major body structures are eventually formed from each germ layer?

Answer 14

ECTODERM: Epidermis, hair, nails, cutaneous and mammary glands; central and peripheral nervous system
MESODERM: Paraxial: Muscles of head, trunk, limbs, axial skeleton, dermis, connective tissue; Intermediate: Urogenital system, including gonads; Lateral: Serous membranes of pleura, pericardium, and peritoneum, connective tissue and muscle of viscera, heart, blood cells
ENDODERM: Epithelium of lung, bladder and gastrointestinal tract; glands associated with G.I. tract, including liver and pancreas.

Question 15

How does the trophoblast become transformed into chorion and placenta?



Answer 15

Magic, or, in certain cases, witchcraft.

Question 16

What is the notochord, and what two of its main functions?

Answer 16

The rostral-most epiblast cells that migrate toward and through the primitive streak are channeled through the anterior swelling of the streak - Hensen’s node. Many cells which migrate through Hensen’s node and descend into the mesoderm subsequently migrate rostrally and form a thick cord of cells called the notochord. Toward the end of gastrulation, the primitive streak regresses, and as it regresses, the notochord lengthens. The notochord is an immensely important structure in the early embryo: it lends longitudinal mechanical support to the embryo, but - most importantly - is serves as a powerful inductive force on the subsequent differentiation of many cell types. Notably, it is the prime inducer of nervous system development. Eventually, the vertebral column forms around the notochord.

Question 17

What is the neural plate?

Answer 17

The first stage of nervous system formation occurs when epiblast (ectoderm) cells directly overlying the notochord are induced by the notochord to proliferate and to form a thickening called the neural plate. By about the 18th day, the neural plate begins to buckle, forming neural folds.

Question 18

What are somites?

Answer 18

The paraxial mesoderm gives rise to somites, which are periodic thickenings that occur along the length of the paraxial mesoderm. They begin to form at about the time of neurulation (the third week). They form in pairs, one on each side of the notochord, and eventually 42 to 44 pairs are formed by the end of the fifth week. The
somites give rise to most of the axial skeleton and associated musculature, and the adjacent dermis of the skin.

Question 19

Neural folds?

Answer 19

By about the 18th day, the neural plate begins to buckle, forming neural folds. The neural folds at the cranial end of the embryo enlarge, and will ultimately form the brain. By the end of the 3rd week, the neural folds have
curved around
and fused to form
a tube, called the
neural tube.

Question 20

Neural tube?

Answer 20

neural folds have fused
ectoderm fully enclosed
end of the third week

Question 21

How does the neural crest and its derivatives form, and what structures do they give rise to?

Answer 21

At the time the neural tube is forming, a population of cells, the neural crest cells, detach from the lateral border of the folds, and actively begin to migrate within the embryo. The neural crest cells eventually give rise to a number of structures, including the spinal and autonomic ganglia, Schwann cells, the meninges, the adrenal medulla, and melanocytes. Because of this, they are sometimes referred to as the “fourth germ layer.”

Question 22

What are epithelial-to-mesenchymal and mesenchymal-to-epithelial transitions?

Answer 22

gastrulation and neural crest cell migration. Both instances involve an epithelial-to-mesenchymal transition (MET).
Snail (a transcription factor) represses cadherin, claudin and occludin expression, which results in loss of adherens and tight junctions.
Matrix metalloproteinase and vimentin expression is increased. These promote the detachment of cells from an epithelium and convert them into mesenchymal-like cells able to invade the extracellular matrix.

Question 23

Specific Binding

Answer 23

Specific binding is a criteria for both strength of interaction and selectivity. Different biological systems depend on different binding stringencies. Antibodies must precisely identify pathogens while ignoring self material.
Tell A from B

Question 24

Affinity

Answer 24

very tight interaction at one small region. How well you hold it

Question 25

Avidity

Answer 25

several interactions that resemble a zipper Cooperative interactions The sum of many tiny binding sites yield very high binding strength.

Question 26

PAMP

Answer 26

Pathogen Associated Molecular Patterns imunogen Molecular moieties (i.e. parts) that are absolutely required for pathogen survival Recognition system has co-evolved with the appearance of the PAMP ``` Examples Endotoxin Flaggelin dsRNA CpG DNA Peptidoglycan Terminal mannose ```

Question 27

DAMP

Answer 27

``` Damage Associated Molecular Patterns imunogen Occult and obscured from the defense mechanisms Danger signal Damage signal Recognized by the Innate immune system Examples Proteins Heat Shock proteins Non-Proteins Uric acid crystals ATP DNA Heparin sulfate Hyaluronan fragments S100 molecules ```

Question 28

Toll-like Receptor

Answer 28

Toll Like receptors are surface molecules with recognition sites for PAMPs, DAMPs and other soluble factors that bind PAMPS (i.e. MD-2/CD14/LBP)). Nine different TLRs have been identified. Three are found in the endosomal compartments of phagocytic cells (e.g. Neutrophils, Macrophage, Dendritic Cells and B-cells). Six are expressed on the cell surface as dimers (homodimers or heterodimers). The TLRs initiate danger signals using the transcription factors NF-κB (Inflammation) and IRF3 (Viral response, increase MHC class I expression)

Question 29

Natural Immunization Artificial Immunization Passive Immunization Active Immunization

Answer 29

know 'em

Question 30

T-cell receptors

Answer 30

T cells express surface receptors that weakly recognize peptides Peptides must be displayed for detection T cells screen mDCs for Ag A match results in T cell activation

Question 31

Positive Selection

Answer 31

``` In order to be positively-selected, thymocytes will have to interact with several cell surface molecules, MHC, to ensure reactivity and specificity.[3] Positive selection selects cells with a T cell receptor able to bind MHC class I or II molecules with at least a weak affinity. This eliminates (by a process called "death by neglect") those T cells which would be non-functional due to an inability to bind MHC. ```

Question 32

Negative Selection

Answer 32

Negative selection is the active induction of apoptosis in thymocytes with a high affinity for self peptides or MHC. This eliminates cells which would direct immune responses towards self-proteins in the periphery. Negative selection is not 100% effective, some autoreactive T cells escape thymic censorship, and are released into the circulation.

Question 33

What is the difference between mosaic and regulative development?

Answer 33

In regulative development, blastomeres initially have similar developmental potencies, each capable of giving rise to a complete embryo. The process of differentiation is responsive to environmental signals, which allows the developmental program to respond and adjust to various types of perturbations. In mosaic development, cell fate is already assigned during cleavage, and a strict developmental plan is in place, whereby removal of one or more cells results in an incomplete embryo. Cell fate is usually determined by the differential inheritance of specific factors among daughter cells during cell divisions, in a process called asymmetric cell division.

Question 34

What is the mechanism by which identical (monozygotic) twins are produced?

Answer 34

Occasionally, the cells of early embryos fail to adhere together normally, and can fall apart into two (or more) masses. Each mass is able to give rise to an entire individual if it occurs early enough Splitting can occur as early as the 2-cell stage, and as late as the blastocyst stage. The later splitting occurs, the greater the chance it will not be complete, and the twins will be conjoined (not completely separated).

Question 35

Define totipotent

Answer 35

can give rise to all embryonic and extra-embryonic cell types and structures

Question 36

Define pluripotent

Answer 36

can give rise to all embryonic cell types and structures

Question 37

Define multipotent

Answer 37

can give rise to multiple (but not all) cell types

Question 38

Define unipotent

Answer 38

can give rise to just one type of cell

Question 39

What is induction?

Answer 39

the ability of one cell (or some type of environmental signal) to influence the development of another cell. Cells are not 'born different,' but instead become different by receiving distinct environmental signals. This leads to a regulative pattern of development, where not only does removal of cells from an early embryo not result in missing body parts (because cell fates take longer to be instructed), but a single cell from an early embryo is able to give rise to an entire organism. This process is most obvious in higher animals, including humans.

Question 40

What are morphogens

Answer 40

Induction: the process where one cell or group of cells changes the developmental fate of another group Signals that alter cell fate are called morphogens Cells producing signals are the inducers Cells receiving the signals must be competent to respond to the signal Instructive: cell “a” gives signal, causing specification and differentiation of cell “b” Permissive: cell “b” already specified, but a signal from “a” allows differentiation to proceed- extracellular matrix interactions are commonly of this type

Question 41

Compare paracrine, juxtacrine, and autocrine signaling

Answer 41

Paracrine: involves diffusable molecules Juxtacrine: Involves cell-cell contact Autocrine: Cells stimulate themselves

Question 42

Compare the different patterns of gradient, antagonist, cascade, and combinatorial signaling

Answer 42

gradient: signa decreases over distance antagonist: one morphogen on one side, competing morphogen on the other side cascade: morphogen hits cell, causes it to produce more morphogens to pass on the signal combinatorial: two morphogens, working together in proportions

Question 43

How are trophoblast vs. inner cell mass fates determined?

Answer 43

Signals from the polarized outer cells (including plasma membrane and cytoskeleton) inhibit Mst1/2 phosphorylation of Yap, allowing active Yap to translocate into the nucleus and activate Tead4 transcription factors, which activate genes associated with proliferation, differentiation, and development, stimulating trophoblast formation. These genes include Cdx2, which is a transcription factor that appears to drive trophoblast formation. The hippo pathway remains active in the unpolarized inner cells, maintaining Yap and Tead4 inhibition.

Question 44

How does epiblast and hypoblast formation progress?

Answer 44

Initially, all blastomeres express Oct4 and Nanog, transcription factors associated with pluripotency and stem cell function. Cdx2 becomes expressed solely in trophoblast cells via inhibition of Hippo signaling. Cells of the inner cell mass maintain Hippo signaling and express Oct4, Nanog, and Gata. Oct4/Nanog and Cdx2/Gata inhibit each other’s expression, creating a double-negative feedback loop. Because of the reciprocal inhibition of Oct4/Nanog and Cdx2/Gata, inner cells end up expressing EITHER Oct 4 and Nanog, OR Gata – but not both. By an incompletely understood mechanism, Gata-positive cells segregate out to form the hypoblast.

Question 45

How are sonic hedgehog, nodal, lefty, and homeobox genes involved in these processes? (Axes determination)

Answer 45

sonic: secreted by notochord in dorsal/ventral nodal/lefty: The exact mechanism is still being worked out, but leftward fluid flow from the node increases the expression of the signaling molecule Nodal on the left side of the embryo. Nodal stimulates the production of itself and another signaling molecule called Lefty, which is antagonistic to nodal (nodal and lefty both belong to the TGF-b family). Not enough lefty is produced to inhibit nodal on the left side, but it is enough to inhibit the lesser amounts of nodal expressed on the right side. Nodal stimulates the production of Pitx2, a transcription factor that modulates gene expression patterns associated with l-r asymmetry. homeobox: Arranged in the same general order on chromosome as ant-post axis

Question 46

How are signaling pathways related to the the regulation of gene expression?

Answer 46

Secreted signaling molecules play central roles in mediating inductive events – for example, FGF (fibroblast growth factor) in eye formation, and Shh (sonic hedgehog) and BMP (bone morphogenetic protein) in neuronal differentiation. A common mechanism of action is that secreted paracrine factors induce target cells to produce different sets of transcription factors, which then specify cell fates.

Question 47

What are the 'big five' signaling pathways involved in morphogenesis, and what are their basic features?

Answer 47

TGF pathway (transforming growth factor; includes TGF and BMP proteins) Hedgehog pathway (sonic hedgehog is the protein mammals express) FGF pathway (fibroblast growth factor; includes a number of FGFs) Wnt pathway Notch pathway

Question 48

How is cell migration and cell adhesion involved in morphogenesis?

Answer 48

know this

Question 49

How do cadherins function in this process? (morphogenesis)

Answer 49

Selective cell-cell adhesion is mediated by cadherins that are expressed in tissue-specific patterns

Question 50

How is the metastatic spread of cancer like the cell movements that occur in embryogenesis?

Answer 50

know this

Question 51

What is chemotaxis?

Answer 51

movement according to certain chemicals in the environment

Question 52

Asymmetric cell division

Answer 52

unequal partitioning of specific factors among daughter cells during cell division. Essentially, daughter cells are 'born different,' resulting in the assignment of different fates as daughter cells are produced. This process is very obvious in lower animals.

Question 53

Brief Summary of Early Developmental Events

Answer 53

Trophoblast/inner cell mass formation (induced by peripheral and cytoskeletal signals via Hippo pathway) Formation of a epiblast and hypoblast (accompanied by differential expression of Oct4, Nanog, and Gata transcription factors) Formation of ectoderm, mesoderm and endoderm via gastrulation Formation of specific tissues and organ rudiments from cells of the different germ layers, which achieve their adult organization through embryo rolling and folding. These events reflect two fundamental processes: A progressive restriction of cell fate Extensive cell motility and migration events

Question 54

Potencies of trophoblasts and epiblasts

Answer 54

Trophoblast cells can only give rise to extraembryonic tissues, and only epiblast cells give rise to all of the cells of the fetus; thus, these cells are associated with different potencies.

Question 55

Dorsal-ventral axis formation

Answer 55

Initially, the neural tube resembles a homogeneous collection of cells which are committed to a neural fate, but not yet specified to a particular type of neural cell. This changes when the notochord induces the ventral floor plate to secrete sonic hedgehog (Shh), and when the overlying ectoderm induces the dorsal roof plate to secrete BMP. The apposing gradients formed instruct the cells in between to express particular transcription factors (like Pax6, Pax7, and NKx6.1), and adopt specific fates. As with eye development, there are additional positional signals that come into play. Another fundamentally important family of transcription factors that is involved in instructing positional identity along the anterior-posterior axis are the Homeobox (or Hox) genes. This gene family has been shown to be responsible for body patterning in organisms as diverse as fruit flies and humans.

Question 56

Left-right axis formation

Answer 56

A surprising clue to l-r axis determination was the discovery that dynein mutants/knock-outs exhibit random placement of asymmetric organs. It was then discovered that ciliary cells of the primitive node establish directional fluid flow from right-to-left (by all beating in the same direction). The exact mechanism is still being worked out, but leftward fluid flow from the node increases the expression of the signaling molecule Nodal on the left side of the embryo. Nodal stimulates the production of itself and another signaling molecule called Lefty, which is antagonistic to nodal (nodal and lefty both belong to the TGF-b family). Not enough lefty is produced to inhibit nodal on the left side, but it is enough to inhibit the lesser amounts of nodal expressed on the right side. Nodal stimulates the production of Pitx2, a transcription factor that modulates gene expression patterns associated with l-r asymmetry.

Question 57

Anterior-posterior axis formation

Answer 57

Hox genes – Homeobox genes Involved in anterior-posterior axis formation Organized in a gene complex of 13 genes (repeated 4 times on different chromosomes; HoxA, B, C and D) Encode transcription factors that contain homeodomains: a DNA-binding sequence of 60 amino acids Arranged in the same general order on chromosome as ant-post axis RA appears to be involved in regulating Hox expression; Exogenous retinoic acid (RA) can disrupt normal patterns of Hox gene expression RA found in the primitive node; the longer cells are reside in the node (exposed to RA), the more posterior fate they adopt.

Question 58

List and explain the adaptive responses to physiologic stimuli and injurious stimuli

Answer 58

hypertrophy, hyperplasia, atrophy, and metaplasia

Question 59

Describe the gross patterns and microscopic findings of tissue necrosis

Answer 59

Morphologic appearance of necrosis is due to denaturation of intracellular proteins and enzymatic digestion of lethally injured cells ``` Microscopic changes of individual cell necrosis: Increased cytoplasmic eosinophilia in tissue stains (hematoxylin and eosin) Myelin figures (dead cell replaced by mass of damaged cell membranes) Nuclear changes: karyolysis (nucleus fades away), pyknosis (shrunken nucleus, can also be seen in apoptosis), karyorrhexis (pyknotic nucleus undergoes fragmentation) ``` Key point: necrotic cells are unable to maintain membrane integrity and their cell contents can leak out; cell specific proteins and enzymes can be detected in the blood, and this is the rationale for using diagnostic tests to detect the presence of organ specific tissue necrosis (e.g. myocardial infarct, liver damage)

Question 60

List the causes and describe the mechanisms of cell injury

Answer 60

Depletion of ATP Mitochondrial damage Influx of calcium and loss of calcium homeostasis Accumulation of oxygen-derived free radicals Defects in membrane permeability Damage to DNA and proteins

Question 61

Define apoptosis, and describe the typical microscopic findings. Which enzyme pathway is typically activated in apoptosis?

Answer 61

Apoptotic cells demonstrate: Activation of caspases (cysteine proteases) DNA and protein breakdown Membrane alterations with enhanced recognition by phagocytes Morphologic features of apoptotic cells include: Cell shrinkage Condensation of nuclear chromatin Formation of blebs and fragments (apoptotic bodies) Phagocytosis, usually by macrophages In tissue sections, apoptotic cells are typically shrunken, and appear as a round or oval mass of eosinophilic cytoplasm with fragments of condensed, often fragmented nuclear chromatin Key point: apoptosis and necrosis often appear together

Question 62

Describe the four mechanisms of intracellular accumulations, and list some examples discussed in class.

Answer 62

abnormal metabolism defect in protein folding/transport lack of enzyme ingestion of indigestible materials Some examples: Fatty change of the liver, associated with alcohol abuse or nonalcoholic fatty liver disease Cholesterol or cholesterol esters, associated with atherosclerotic vascular disease; patients can get accumulation of cholesterol within dermal macrophages (xanthomas) Proteins can accumulate in a variety of conditions: Reabsorption droplets in proximal renal tubules seen in renal diseases with protein loss Excessive protein production, such as Russell bodies in plasma cells Defective secretion of proteins, such as alpha-1-antitrypsin deficiency Accumulation of cytoskeletal proteins, such as Mallory bodies in the liver in fatty liver disease Aggregation of abnormal proteins, such as amyloidosis Hyaline change is a microscopic descriptive term for eosinophilic glassy protein which can be seen in a variety of conditions Glycogen can accumulate in various cells in patients with diabetes; patients with glycogen storage diseases (genetic enzymatic defects of glycogen metabolism) can have massive accumulations of glycogen. Exogenous pigments (anthracosis, tattoo) Endogenous pigments: Lipofuscin (brown lipid), results from free radical injury and lipid peroxidation of subcellular membranes – seen in liver and heart as part of aging process, malnutrition, cancer cachexia Melanin (skin) Hemosiderin granules, which are aggregates of ferritin, a protein iron complex. The common bruise is an example of localized hemosiderosis. Systemic hemosiderosis can occur in disorders resulting in systemic overload of iron

Question 63

Describe the two types of pathologic calcification.

Answer 63

Dystrophic calcifications (normal serum calcium level): Can occur in areas of necrosis with deposition of crystalline calcium phosphate; can get heterotopic bone formation Often seen in association with atherosclerosis, damaged heart valves, fat necrosis, tuberculosis Metastatic calcification: Due to hypercalcemia secondary to disordered calcium metabolism (elevated serum calcium) Calcium phosphate is deposited in normal tissues (lung, kidney (nephrocalcinosis), gastric mucosa, systemic arteries, pulmonary veins); can get heterotopic bone formation Four principal causes of hypercalcemia are: -Increased parathyroid hormone production (PTH) -Destruction of bone tissue -Renal failure (phosphate retention, secondary hyperparathyroidism) -Vitamin D related disorders

Question 64

In your own words, describe cellular aging.

Answer 64

Commen da ne talomares ca nepho melandra ca. Cellular aging is the result of a progressive decline in cellular function and viability caused by genetic abnormalities and the accumulation of sub lethal cellular and molecular damage due to effects of exposure to exogenous influences Aging is a regulated process, controlled by a limited number of genes Changes which contribute to aging include: Decreased cellular replication: after a fixed number of divisions all somatic cells become arrested in a terminally non-dividing state known as senescence. Telomere shortening may play a role. Accumulation of metabolic and genetic damage The causes of aging, as well as strategies for reducing aging, are very active areas of research

Question 65

Using examples discussed in class, explain the rationale for measuring biomarkers of cellular necrosis.

Answer 65

AST (aspartate aminotransferase): Present in the liver as well as heart, skeletal muscle, brain, and kidneys. Elevation is not specific for the liver. ALT (alanine aminotransferase): Only small amounts are found in tissues other than the liver, so ALT is a more specific indicator of hepatocyte injury than AST. Tests that establish the presence of bile duct damage: Alkaline phosphatase (ALP): Consists of various isoenzymes found in bone, liver, placenta, intestine, and leukocytes. Increase is usually due to bone or liver disease. Measurement of gamma-glutamyl transferase (GGT, associated with biliary epithelium) can assist in determining if ALP rise is due to bone or liver. Comprehensive metabolic profile (a group of laboratory tests) typically includes AST, ALT, and alkaline phosphatase. Elevation of cardiac troponin I typically reflects damage to cardiac muscle:

Question 66

Hypertrophy

Answer 66

Increase in the size of cells, resulting in increase in the size of the organ. Can be physiologic or pathologic. Results from increased production of cellular proteins. Selective hypertrophy can occur at the level of the subcellular organelle (e.g. smooth endoplasmic reticulum).

Question 67

Hyperplasia

Answer 67

Increase in the number of cells, resulting in an increase in the size of the organ. Occurs if the cells of the organ can divide. Can be physiologic (hormonal or compensatory) or pathologic (excesses of hormones or growth factors); new cells may arise from mature cells or tissue stem cells.

Question 68

Atrophy

Answer 68

Decrease in cell size and number, resulting in reduced size of a tissue or organ. Can be physiologic or pathologic. Common causes of pathologic atrophy are: Decreased workload Loss of innervation (denervation atrophy) Diminished blood supply Inadequate nutrition Loss of endocrine stimulation Pressure Results from decreased protein synthesis and increased protein degradation within the cells; increased autophagy may also be involved (“self-eating” – autophagic vacuole fuses with a lysosomal vacuole, thereby digesting cellular components with the formation of residual bodies (such as lipofuscin granules)

Question 69

Metaplasia

Answer 69

Reversible change in which one differentiated type of cell is replaced by another cell type. Results from the reprogramming of stem cells present in normal tissue or reprogramming of undifferentiated mesenchymal cells. External stimuli promote expression of genes that lead to a specific differentiation pathway. Many examples exist: Columnar to squamous (squamous metaplasia) Squamous to columnar (Barrett esophagus) Connective tissue metaplasia Key point: influences that predispose to metaplasia, if persistent, may lead to malignant transformation (e.g. Barrett esophagus leading to adenocarcinoma).

Question 70

types of necrosis

Answer 70

Coagulative necrosis: Architecture of dead tissue is preserved (infarct) Liquefactive necrosis: Digestion of the dead tissue results in liquid viscous mass; typically seen in focal bacterial or occasionally fungal infections, the microbes stimulate the accumulation of neutrophils which liberate tissue destroying enzymes, resulting in creamy necrotic material filled with neutrophils (pus) Gangenous necrosis: Clinical term, not specific pattern, usually applied to necrosis of a limb undergoing coagulative ischemic necrosis Caseous necrosis: Cheeselike necrosis associated with necrotizing granulomas, seen with tuberculosis and fungal infections Fat necrosis: Refers to focal areas of fat destruction Fibrinoid necrosis: Pattern of necrosis seen in immune reactions involving vessels

Question 71

Depletion of ATP

Answer 71

ATP is required for virtually all synthetic and degradative processes in the cell (e.g. membrane transport, protein synthesis) Major causes of ATP depletion are reduced blood supply of oxygen and nutrients, mitochondrial damage, exposure to certain toxins (e.g. cyanide) Depletion of ATP to 5-10% of normal levels has widespread effects on the cell. These effects include: -Failure of plasma membrane energy-dependant sodium pump (cell swelling) -Altered energy metabolism (reduced oxidative phosphorylation, increased anaerobic glycolysis, increase in lactic acid – lab test!) -Calcium pump failure -Disruption of ribosomes with reduced protein synthesis; also get misfolded proteins (unfolded protein response) -Eventually get irreversible damage and cell death

Question 72

Mitochondrial damage

Answer 72

Mitochondria supply ATP to the cell thru oxidative phosphorylation Mitochondria can be damaged by oxygen deprivation, oxygen free radicals, increased cytosolic calcium Mitochondrial damage results in: - Defect in the mitochondrial membrane (mitochondrial permeability transition pore) which leads to failure of oxidative phosphorylation and depletion of ATP - Escape of mitochondrial membrane proteins which can activate apoptotic pathways (cytochrome c)

Question 73

Influx of calcium and loss of calcium homeostasis

Answer 73

Cytosolic free calcium is normally maintained at a very low level compared to extracellular calcium levels; when injured, calcium is released from intracellular stores and the cell membrane becomes more permeable to extracellular calcium Increased intracellular calcium results in: - Mitochondrial membrane defect and failure of ATP generation - Activation of lytic enzymes (phospholipases, proteases, endonucleases, ATPases) - Induce apoptosis (activate caspases)

Question 74

Accumulation of oxygen-derived free radicals (oxidative stress)

Answer 74

Free radicals are chemical species that have a single unpaired electron Reactive oxygen species (ROS) refer to types of oxygen-derived free radicals that are produced normally in the cell during mitochondrial respiration and energy production; cellular defense mechanisms are in place to remove ROS and maintain a steady state with no cell damage When the production of ROS increases or the scavenging systems are ineffective, ROS increases with an increase of free radicals (oxidative stress) Oxidative stress has been implicated in a wide variety of conditions and diseases (cancer, aging, degenerative diseases)

Question 75

Defects of membrane permeability

Answer 75

Membrane damage can occur as a result of: - Reactive oxygen species - Decreased phospholipid synthesis - Increased phospholipid breakdown - Cytoskeletal abnormailities (cell stretching) Membrane damage results in: - Mitochondrial membrane damage (decreased ATP, apoptosis) - Loss of osmotic balance and loss of cellular components - Injury to lysosomal membranes with release of lytic enzymes with enzymatic digestion of proteins, RNA, DNA, glycogen

Question 76

Damage to DNA and proteins

Answer 76

Cells have mechanisms to repair DNA, but if the damage is too severe, the cell will initiate enzymatic programs that result in death by apoptosis Misfolded proteins, the result of genetic mutations or acquired through cell injury, can also result in apoptosis

Question 77

irreversibility is typically characterized by

Answer 77

Inability to reverse mitochondrial dysfunction | Profound disturbances in membrane function

Question 78

Chemical (toxic) injury

Answer 78

Injury occurs either by direct toxic effect, or through the toxic effects of a metabolite; many mechanisms exist, including damaging cell membranes, production of free radicals, enzyme disruption (e.g., cyanide poisons mitochondrial cytochrome oxidase and inhibits oxidative phosphorylation) As the liver is often involved in the metabolism of drugs and toxins, it is a frequent target of drug toxicity

Question 79

What are the two fundamental characteristics of stem cells?

Answer 79

Stem cells are not terminally differentiated, but can give rise to daughter cells that can terminally differentiate. Stem cells can self-renew by dividing and producing two daughter cells, at least one of which does not enter the differentiation pathway, but remains a stem cell. Stem cells self-renew in order to sustain long-term tissue regeneration

Question 80

What are the usual proliferative potentials of stem cells, progenitor cells, and terminally differentiated cells?

Answer 80

stem cells: unlimited progenitor cells: limited terminially differentiated cells: hayflick limit?

Question 81

What mechanisms help protect stem cell DNA?

Answer 81

Since the process of DNA replication is not perfect and can result in the introduction of genomic changes, the use of progenitor cells as an amplifying system keeps the number of stem cells that are needed low, so the number of divisions they need to make is much reduced (even when the demand for cells is high), reducing the potential for genetic damage. Remarkably, stem cells appear to have the ability to specifically segregate their replicated chromosomes so that the daughter cell that remains a stem cell receives all of the parental chromosome template strands. This has been called the 'immortal strand hypothesis,' and is supported by a number of experimental approaches. The inheritance of all of the 'template' strands of DNA in a daughter cell reduces the chances of their being altered during synthesis (because they were used as a template only – and not assembled nucleotide by nucleotide).

Question 82

Why does stem cell DNA have to be protected to a greater degree than that of normal somatic cells?

Answer 82

Because stem cells are the reserve cells that are used to replenish tissues and organs, it is important to protect them from genomic damage, particularly as they may be held in reserve for many years until needed.

Question 83

Compare and contrast the potency and availability of embryonic and adult stem cells.

Answer 83

Embryonic: Are usually isolated from the inner cell mass or epiblast of blastocysts. Cells at this stage are capable of developing into all cell types of the body, and so are pluripotent. Advantages: Pluripotent, rapid division rate, and source is well defined (inner cell mass). Disadvantages: Ethical issues involving destruction of embryo. For example – there are a lot of excess embryos produced in IVF clinics; tens of thousands of frozen embryos are thrown away when couples finish their treatment. Adult: Involved in replacing and repairing tissues in a particular organ. Can typically form only a limited subset of cell types, and so are usually either multipotent or unipotent. Advantages: Ethical issues related to embryo use avoided. Disadvantages: Multipotent at best. Difficult to identify, isolate, and purify as they are rare - estimated at 0.1-3% of cells. Have a low rate of cell division, and so do not proliferate readily

Question 84

What are mesenchymal stem cells?

Answer 84

Mesenchymal Stem Cells (MSCs) – a type of adult stem cell found in bone marrow (as well as other places in the body). Are identifiable, readily obtainable, and experimentally tractable MSCs are multipotent adult stem cells Found in several adult tissues as well as umbilical cord Able to give rise to numerous mesenchymal cell types including bone, cartilage, muscle, and fat.

Question 85

What are iPS cells, and how are they produced?

Answer 85

induced pluripotent cells. These are cells produced by transfection and enforced expression of a small number of transcription factors (e.g., Oct4, Nanog, and others). However, these are difficult to produce, and have been shown to occasionally give rise to tumors when injected into animals. A significant improvement may be the use of miR-302 to produce iPS cells.

Question 86

How do primordial germ cells compare with stem cells?

Answer 86

a

Question 87

What is SCNT (somatic cell nuclear transfer)?

Answer 87

Because of the ability of a zygote to develop totipotency and subsequently give rise to a complete individual, researchers a number of years ago sought to determine what factors were responsible. One experiment was to remove the nucleus of an egg, and add a nucleus from an adult, somatic cell. The egg was then activated to divide, and resulting daughter cell behavior studied. This type of experimental approach is called SCNT, for somatic cell nuclear transfer.

Question 88

How are Oct4 and Nanog related to potency?

Answer 88

. The model is that miR-302 suppresses the expression of epigenetic modulators (methyltransferases, etc.), resulting in global demethylation and reactivation of the genome, including Oct4 and Nanog expression. Oct4 and Nanog themselves further promote miR-302 expression, constituting a positive feedback loop that promotes pluripotency. At some point, expression of other gene products occur in response to environmental signaling that suppress Oct4 and Nanog expression, leading to a downregulation of miR-302 and the initiation of epigenetic methylation, gene silencing, and a restriction of developmental potential.

Question 89

How is gene expression epigenetically regulated during the progressive restriction of cell fate that occurs during early development?

Answer 89

a

Question 90

At what two points in the human life cycle does global demethylation occur?

Answer 90

1. Shortly after fertilization (preimplantation reprogramming) - demethylation is incomplete, with methylation at imprinted regions being maintained; this allows the zygote to attain totipotency while still allowing for paternally- and maternally-derived genes to be differentially expressed (due to imprinting). 2. During primordial germ cell (PGC) determination – here, demethylation is complete, in order to allow for a resetting (erasing) of imprinted regions according to the sex of the embryo. Subsequently, specific genes are imprinted in sex-specific patterns during spermatogenesis and oogenesis.

Question 91

How is this (global demethylation) related to the pluripotency of early embryonic cells, iPS cells, and primordial germ cells/germ cell tumors?

Answer 91

a

Question 92

What is the stem cell niche, and what are some examples of how signaling pathways are involved in the regulation of the niche?

Answer 92

Wnt signaling in the crypt is critical in maintaining cell proliferation in the crypt, and Notch signaling is involved in the differentiation of progenitor cells into the different cell types of the villus (absorptive cells, goblet cells, etc.). The stem cell niche appears to be created by an interplay of Wnt, Hedgehog and BMP signaling, where Wnt and Hedgehog induce the connective tissue cells in the core to produce BMP4, which acts to restrain niche localization to the crypts (if BMP signaling is blocked, aberrant crypts form further up the villus).

Question 93

What are some applications of stem cell technology to regenerative medicine?

Answer 93

Stem cell technology has enormous potential in regenerative medicine. In addition to obvious applications repairing damaged tissues and organs (e.g., from burns or heart attacks), let your imagination run wild about how they might be used…

Question 94

What are some applications of stem cell technology to reproductive biology?

Answer 94

How about helping infertile couples to have children genetically derived from them? What if one could take, say, some skin cells from two patients, reprogram them to pluripotency, then direct the iPS cells from the male to differentiate into sperm, and iPS cells from the female to differentiate into oocytes? Then, use these gametes to produce a zygote that could be implanted into the female to produce a healthy baby.

Question 95

What are some applications of stem cell technology to cloning?

Answer 95

In therapeutic cloning the embryo produced by SCNT is not placed in a host mother, but dissociated and grown in a culture dish to provide pluripotent cells for regenerative medicine uses

Question 96

List and describe the five cardinal signs of inflammation

Answer 96

``` Redness: rubor Swelling: tumor Heat: calor Pain: dolor Loss of function ```

Question 97

List and describe the key stimuli for acute inflammation.

Answer 97

Infections Receptors recognize microbes and microbial products, triggering signaling pathways Tissue necrosis Ischemia, trauma, chemical or thermal injury, irradiation lead to release of molecules from dead cells which elicit the inflammatory response Foreign bodies Splinters, dirt, sutures elicit inflammation and carry microbes Immune reactions (hypersensitivity reactions) These are reactions in which the normally protective immune system damages the individual’s own tissues These reactions can be directed against self antigens (autoimmune diseases) or can be excessive reactions against environmental substances or microbes These reactions are often persistent and cannot be cured, leading to disease; these disorders are often referred to as immune-mediated inflammatory disease

Question 98

List and describe the three major components of the acute inflammatory response.

Answer 98

Acute inflammation is a rapid host response to deliver leukocytes and plasma proteins (antibodies) to the sites of infection and injury Acute inflammation has three major components: Alterations in vascular caliber that increase blood flow Structural changes in the microvasculature that allow plasma proteins and leukocytes to leave the circulation Emigration of leukocytes from the microcirculation, accumulation at the site of injury, and removal of the offending agent

Question 99

List and describe the three key steps involved in extravasation of neutrophils.

Answer 99

Leukocyte adhesion to endothelium: this involves leukocyte margination, rolling, and adhesion to the endothelium: -Margination (leukocytes in a peripheral position) occurs secondary to the effects of stasis Adhesion of leukocytes to the endothelium is mediated by complementary adhesion molecules on the two cell types, enhanced by secreted proteins called cytokines -Rolling occurs as the leukocytes transiently adhere to the endothelial surface -Eventually leukocytes firmly adhere to the endothelium and stop rolling -Rolling interactions are mediated by proteins called selectins, which bind to sialylated oligosaccharide ligands; expression of selectins and the ligands is mediated by cytokines (tumor necrosis factor (TNF), interleukin 1 (IL-1), released by tissue macrophages, mast cells, and endothelial cells in response to microbes and dead tissues; these cells also release chemokines (chemoattractant cytokines) -Firm adhesion is mediated by surface proteins on the leukocyte called integrins; expression is enhanced by cytokines, and along with the action of chemokines, the leukocytes bind to the endothelium at the site of inflammation Leukocyte migration through the endothelium and into the extracellular space: -This is called transmigration or diapedesis -Mediated by chemokines -Once in the connective tissue, leukocytes adhere to the extracellular matrix by virtue of integrins and CD44 binding to matrix proteins. Thus the leukocytes are retained at the site where they are needed! Genetic disorders: Leukocyte adhesion deficiency type 1: defect in biosynthesis of integrins Leukocyte adhesion deficiency type 2: absence of sialyl-Lewis X, the ligand for selectin Chemotaxis of leukocytes: - Chemotaxis is locomation oriented along a chemical gradient - Exogenous chemoattractants include bacterial products - Endogenous chemoattractants include cytokines, components of the complement system (C5a), and arachidonic acid (AA) metabolites, mainly leukotriene B4 - The chemotactic agents bind to the surface of the leukocyte, induce the polymerization of intracellular actin, resulting in leukocyte locomotion

Question 100

Discuss the mechanisms by which leukocytes recognize microbes and dead tissue,

Answer 100

Leukocytes express receptors that recognize external stimuli; once bound to these receptors, activating signals are delivered to the leukocyte. These receptors include: G protein coupled receptors receptors for opsonins receptors for cytokines

Question 101

Explain the key cell derived and protein derived mediators of the inflammatory response.

Answer 101

Mediators are derived either from cells or plasma proteins; cell derived mediators are often sequestered in intracellular granules which can be rapidly released by exocytosis; principal cell types involved include platelets, neutrophils, monocytes/macrophages, and mast cells Active mediators are produced in response to various stimuli, including microbial products, substances from necrotic cells, and proteins from the complement, kinin, and coagulation systems One mediator can stimulate the release of other mediators, amplifying or counteracting the initial action of the mediator Mediators vary in their range of cellular targets Once activated, most mediators are short lived

Question 102

List and describe the three outcomes of the acute inflammatory response.

Answer 102

Complete resolution: removal of cellular debris and microbes by macrophages, and resorption of edema fluid Healing by connective tissue replacement (fibrosis): connective tissue grows into the area of damage or exudate, converting it into a mass of fibrous tissue (this process is also called organization) Progression of the acute inflammatory response to chronic inflammation

Question 103

List and describe the types of conditions or situations that give rise to chronic inflammation

Answer 103

- Persistent infections: viral, mycobacterial, fungal; may get a granulomatous reaction - Immune-mediated inflammatory disease: autoimmune diseases, allergic diseases - Prolonged exposure to toxic agents, exogenous or endogenous: e.g. silicosis, atherosclerosis

Question 104

List and describe the cell types and key functions of the cells involved in chronic inflammation.

Answer 104

Chronic inflammation is characterized by: ``` Inflammation of mononuclear cells: macrophages, lymphocytes, plasma cells (as opposed to neutrophils in the acute inflammatory response) Tissue destruction (without the vascular changes and edema seen in acute inflammation) Attempts at healing with connective tissue replacement of damaged tissue (fibrosis) along with proliferation of small vessels (angiogenesis) ``` Cell types involved in chronic inflammation include: ``` Macrophages Lymphocytes Plasma cells Eosinophils Mast cells ```

Question 105

Define a granuloma, and list and describe the three types of granulomas found in tissues

Answer 105

Granulomatous inflammation is a distinctive pattern of chronic inflammation encountered in a limited number of infectious and non infectious conditions; it is a cellular attempt to contain an offending agent which is difficult to eradicate; typically there is strong activation of T lymphocytes, leading to macrophage activation, resulting in tissue injury A granuloma is a focus of chronic inflammation consisting of a microscopic aggregation of macrophages that are transformed into epithelial-like cells (histiocytes), surrounded by a collar of lymphocytes; variable numbers of plasma cells may also be present ; the epithelial-like cells (histiocytes) may also form giant cells Granulomas can be categorized by their morphologic appearance: - Foreign body granulomas: see foreign material within histiocytes/giant cells, sometimes called “foreign body giant cell reaction” by pathologists - Caseating granulomas: granulomas that induce cell mediated immune response with central necrosis; these are usually associated with infection (e.g. mycobacterial, fungal infections) - Non-caseating granulomas: granulomas that induce cell mediated immune response without central necrosis (e.g. Sarcoidosis, Crohn’s disease)

Question 106

Describe the systemic effects of inflammation

Answer 106

Systemic changes associated with acute inflammation are called the acute phase response. Some of these changes are as follows: Fever: produced in response to substances called pyrogens; bacterial products can act as exogenous pyrogens, stimulating leukocytes to release cytokines such as IL-1 and TNF (endogenous pyrogens); this results in increased activity of cyclooxygenases that convert AA to prostaglandins; in the hypothalamus, the prostaglandins stimulate the production of neurotransmitters which reset the temperature set point to a higher level, which is believed to help the body ward off microbial infections; non-steroidal anti-inflammatory drugs (NSAIDs) and aspirin lower temperature by inhibiting prostaglandin synthesis Acute phase proteins: these plasma proteins, mostly synthesized by the liver, increase greatly as a result of the inflammatory response, either acute or chronic. Some of the key proteins are: C-reactive protein Fibrinogen Serum amyloid A (SAA) protein Increased synthesis of these proteins in the liver results from the release of cytokines as part of the inflammatory response. Prolonged production of SAA protein associated with chronic inflammation can result in secondary amyloidosis. Leukocytosis: inflammatory reactions, especially those produced by bacterial infections, can lead to elevation of the white blood cell count Other systemic effects of the acute phase response: decreased blood pressure with increased pulse, rigors (shivering), chills, anorexia, somnolence, malaise. Some patients can develop profound and life threatening hypotension as a result of the systemic response to bacterial and fungal infections (septic shock). Systemic changes associated with abnormal inflammatory response: Consequences of defective inflammation: increased susceptibility for infections Consequences of excessive inflammation: allergies, autoimmune diseases, atherosclerotic vascular disease

Question 107

exudate vs transudate

Answer 107

- Exudate: extracellular fluid with high protein concentration, cellular debris, and high specific gravity - Transudate: extracellular fluid with low protein concentration, little or no cellular debris, low specific gravity -Presence of exudate implies an increase of normal permeabilty of small vessels in an area of injury (inflammatory reaction); transudate is an ultrafiltrate of fluid that results from osmotic or hydrostatic imbalance across the vessel wall without an increase in vascular permeability - Edema: excess of fluid in the interstitial tissue - Effusion: excess of fluid in a serous cavity - Edema and effusions can be either an exudate or a transudate - Pus (purulent exudate): inflammatory exudate rich in neutrophils, debris of dead cells, and microbes in some cases

Question 108

Discuss the mechanisms by which leukocytes remove offending agents.

Answer 108

Recognition of microbes or dead cells by the recognition receptors described previously lead to leukocyte activation via signaling pathways. The removal of the offending agents involve two steps: Phagocytosis and engulfment: Mannose receptors, scavenger receptors, and receptors for various opsonins (especially IgG antibodies and complement C5a) function to bind and ingest microbes, leading to engulfment of the particle into a phagosome, which then fuses with a lysosomal granule, resulting in a phagolysome Killing and degradation within the neutrophil or macrophage is the final step; microbial killing is accomplished largely by reactive oxygen species (ROS) and reactive nitrogen species (mainly derived from NO), generated within the phagolysosome. This requires a rapid oxidative reaction, called the respiratory or oxidative burst. In neutrophils, the enzyme myeloperoxidase (found in the azurophil granules) creates bactericidal bleach from available chlorine and hydrogen peroxide! Various other constituents are also present in the cytoplasm for microbial killing (elastase, defensins, cathelicidins, lysozymes, lactoferrin, bactericidal/permeability increasing protein); eosinophils contain major basic protein, cytotoxic not to bacteria but cytotoxic to many parasites

Question 109

Histamine

Answer 109

Primarily found in mast cells, and stored as preformed molecules in mast cell granules; also present in basophils and platelets; release is by mast cell degranulaton, as a result of physical injury, binding of antibodies to mast cells (allergic reaction), exposure to fragments of complement called anaphylatoxins (C3a and C5a), and exposure to histamine-releasing products from leukocytes, neuropeptides, and cytokines; histamine causes dilation of arterioles and increased vessel permeability vasoactive

Question 110

Seratonin

Answer 110

Primarily found in platelets, with similar actions to histamine; released when platelets aggregate (clotting) vasoactive

Question 111

Arachidonic Acid (AA) metabolites

Answer 111

When activated by various stimuli, cells can convert membrane bound arachidonic acid into prostaglandins and leukotrienes through the action of enzymes Prostaglandins are produced by many cell types, including mast cells, macrophages, and endothelial cells. They are involved in the vascular response of inflammation but also mediate the systemic reaction (pain and fever). Leukotrienes are primarily secreted from leukocytes and have chemoattractant and vascular effects. The cysteinyl-containing leukotrienes cause vasoconstriction and bronchospasm. Lipoxins are generated from AA and inhibit inflammation Key enzymes involved in the conversion of AA are phospholipases and cyclooxygenase; many anti-inflammatory drugs work by inhibiting these enzymes and thus inhibit the conversion of AA into prostaglandins and leukotrienes (read Robbins pp 59-60, section on anti-inflammatory drugs).

Question 112

Platelet aggregating factor (PAF)

Answer 112

Secreted by platelets, leukocytes, mast cells, and endothelial cells; PAF elicits most of the vascular and cellular reactions of inflammation, as well as vasoconstriction, bronchospasm, and platelet aggregation

Question 113

Reactive oxygen species (ROS)

Answer 113

Can be released extracellularly from leukocytes as part of the acute inflammatory response, following exposure to microbes, chemokines, immune complexes, and phagocytic challenge; production is dependant on the NADPH oxidase system; low extracellular levels amplify the acute inflammatory response; they can also damage endothelium, as well as other cell types, and inactivate proteases (e.g. alpha-1-antitrypsin); host cells, serum, and tissue fluids contain anti-oxidants to protect against these oxygen derived free radicals; tissue damage from ROS is dependant on the balance between production and inactivation of ROS and antioxidants.

Question 114

Nitric Oxide (NO)

Answer 114

Produced by endothelial cells; causes vasodilation, and NO-derived free radicals are microbicidal (and can also damage host cells); NO also inhibits the cellular component of the inflammatory response

Question 115

Cytokines

Answer 115

Cytokines are proteins produced by many cell types (primarily activated lymphocytes and macrophages) that modulate the function of other cell types; they are involved in immune responses, but also involved in both acute and chronic inflammation. Some key cytokines involved in inflammation include tumor necrosis factor (TNF) and interleukin-1 (IL-1). Patients with familial Mediterranean fever have a genetic defect which results in unregulated IL-1 production; these patients present with fever and unprovoked systemic inflammation; treatment is with IL-1 antagonists List of cytokines involved in inflammation continues to grow (IL-6, IL-7)

Question 116

Chemokines

Answer 116

Family of proteins that act as chemoattractants for specific types of leukocytes (neutrophils, monocytes, eosinophils, basophils, lymphocytes); chemokines bind to transmembrane G protein-coupled receptors; they function to stimulate leukocyte recruitment in inflammation and control the normal migration of the cells through various tissues

Question 117

Lysosomal constituents of leukocytes

Answer 117

Neutrophils and macrophages contain a variety of lysosomal enzymes. Many of these are proteases, which can degrade both intracellular (within phagolysosomes) and extracellular components. If leukocyte infiltration is unchecked, further tissue damage can occur. These proteases are held in check by a system of anti-proteases. For example, alpha-1-antitrypsin is the major inhibitor of neutrophil elastase

Question 118

Neuropeptides

Answer 118

Secreted by sensory nerves and leukocytes, they can initiate and propagate the inflammatory response (substance P); along with prostaglandins and cytokines, can also produce pain

Question 119

Complement system

Answer 119

Complement system consists of more than 20 proteins, involved in the immune response for defense against microbial pathogens. In the process of complement activation, cleavage products of complement proteins are elaborated that cause increased vascular permeability, chemotaxis, and opsonization. The inactive complement proteins, when activated, also serve as proteolytic enzymes to activate other complement proteins (complement cascade); in inflammation, some key complement functions include: - Inflammation: C3a, C5a, C4a stimulate histamine release from mast cells and are anaphylatoxins, involved in the immune reaction called anaphylaxis; C5a is also a chemoattractant, and activates the lipoxyganase pathway of AA conversion in neutrophils and macrophages, causing further release of inflammatory mediators - Phagocytosis: C3b when bound to microbial cell wall promotes phagocytosis by neutrophils and macrophages - Cell lysis: complex of C9 on microbial cell wall (known as membrane attack complex) makes cell wall permeable to water and ions and causes lysis C3 and C5 can be cleaved by proteolytic enzymes in the inflammatory exudate, some of which are secreted by neutrophils. These complement proteins have chemoattractant properties, leading to further neutrophil recruitment, creating the potential for a self-perpetuating cycle of neutrophil recruitment. However, the activation of complement is tightly controlled by a variety of cell-associated and circulating regulatory proteins.

Question 120

Coagulation and Kinin systems

Answer 120

Coagulation and Kinin systems are involved in blood clotting Inflammation and blood clotting are often intertwined, with each promoting the other Products of the clotting system can be mediators of the inflammatory response. These include: - Bradykinin, C3a, C5a: mediators of increased vascular permeability - C5a: mediator of chemotaxis - Thrombin: binds to protease-activated receptors, and for endothelial cells, induce the mobilization of P-selectin, production of chemokines and cytokines, expression of adhesion molecules for leukocyte integrins, induction of cyclooxygenase-2 and production of prostaglandins, production of PAF and NO, and changes in endothelial shape

Question 121

MORPHOLOGIC PATTERNS OF ACUTE INFLAMMATION

Answer 121

Morphologic hallmarks are dilation of small blood vessels with vascular congestion and accumulation of leukocytes (neutrophils) and fluid into the extracellular space Acute suppurative inflammation: acute inflammation rich in neutrophils, forming grossly evident pus or purulent (suppurative) exudate (e.g. acute appendicitis) Abscess: localized collection of purulent inflammatory tissue, buried and confined within an organ, tissue, or confined space (basically a pocket of necrotic tissue, filled with pus) Pyogenic (pus-producing) bacteria are bacteria that produce suppurative inflammation (e.g. staphylococci) Ulcer: local defect or excavation of the surface of an organ or tissue that is produced by the sloughing (shedding) of inflamed necrotic tissue (e.g. gastrointestinal tract, skin); ulcers often have evidence of chronicity (chronic inflammation as well as acute inflammation, fibrosis)

Question 122

Macrophages

Answer 122

Derived from blood monocytes; extravasation of blood monocytes begins early in acute inflammation, occurring via the same processes that control neutrophil extravasation; once in the extracellular tissue, the monocyte transforms into a larger phagocytic cell called a macrophage; the macrophage can then be activated when exposed to stimuli (e.g. microbial products, cytokines); the products of activated macrophages eliminate injurious agents and initiate the process of repair, and are responsible for much of the tissue injury in chronic inflammation; because of the activities of macrophages, tissue destruction is one of the hallmarks of chronic inflammation. In acute or short lived inflammation, if the irritant is eliminated, macrophages eventually disappear, either by cell death or into lymphatics; in chronic inflammation, macrophages persist, as there is continuous recruitment from the circulation (macrophages can live for several months or years).

Question 123

Lymphocytes

Answer 123

Lymphocytes are mobilized in both antibody mediated and cell mediated immune reactions; both T and B lymphocytes can migrate into inflammatory sites via interaction with adhesion molecules and chemokines; cytokines and chemokines from macrophages promote lymphocyte recruitment; key point is that both T lymphocytes and macrophages interact in a bidirectional way, so that once the immune system is involved in an inflammatory reaction, the reaction tends to be chronic and severe

Question 124

Plasma cells

Answer 124

Develop from activated B lymphocytes and produce antibodies directed either against persistent foreign or self antigens in the inflammatory site or against altered tissue components. In some cases, the combination of lymphocytes and plasma cells can form structures normally seen in lymph nodes, such as reactive germinal centers.

Question 125

Eosinophils

Answer 125

Eosinophils are abundant in immune reactions mediated by IgE and in parasitic infections. They have granules that contain major basic protein, which is toxic to parasites but also causes lysis within mammalian epithelial cells. Eosinophils are of benefit in controlling parasitic infections, but also contribute to tissue damage in allergies.

Question 126

Mast cells

Answer 126

Widely distributed in connective tissues, and have receptors that bind the Fc portion of the IgE antibody. In immediate hypersensitivity reactions, the IgE antibodies bound to the Fc receptors on the surface of the mast cell recognize the antigen and the mast cells degranulate and release histamine and prostaglandins; this type of reaction occurs in allergic reactions (severe cases can result in anaphylactic shock)

Question 127

sedimentation rate

Answer 127

This test is a nonspecific measure of inflammation. Acute phase proteins such as fibrinogen as well as immunoglobulins can bind to red blood cells (RBCs), causing them to stack (rouleaux). Stacked red blood cells will sediment out faster in a tube of blood than non-stacked RBCs. Values are expressed as mm/hour.

Question 128

C-reactive protein

Answer 128

This test is a sensitive but nonspecific indicator of acute injury, bacterial infection, or inflammation. For example, elevated levels are seen in patients with sepsis, acute appendicitis, pelvic inflammatory disease, and acute myocardial infarction. Elevated CRP is also a risk factor for cardiovascular disease. Values are measured in mg/dl.

Question 129

WBC count and differential.

Answer 129

Leukocytosis refers to an increase in the number of circulating leukocytes (white blood cells, WBCs) in the peripheral blood. The type of WBC that is increased can be a clue to the underlying pathology. For example: Neutrophilia: acute bacterial infections, acute inflammation associated with tissue necrosis (e.g. acute myocardial infarct) Eosinophilia: allergic disorders, parasitic infections, drug reactions, certain malignancies Basophilia: rarely seen, may indicate a myeloproliferative disorder such as chronic myeloid leukemia Monocytosis: chronic infections, bacterial endocarditis, malaria, collagen vascular diseases, inflammatory bowel disease Lymphocytosis: viral infections, Bordetella pertussis infection, disorders associated with chronic immunologic stimulation Performing a “WBC differential” will tell you which type(s) of WBCs are increased. Find your favorite source for list of causes!

Question 130

Define regeneration and repair, and explain the difference between these two terms.

Answer 130

Regeneration: proliferation of cells and tissues following injury, which replaces lost structures; in mammals, only tissues with high proliferative activity can regenerate after injury as long as the stem cells of these tissues are not destroyed (e.g. hematopoietic system, epithelia of the skin and gastrointestinal tract); the term regeneration typically refers to the compensatory growth following injury (e.g. liver following partial hepatectomy). Repair: consists of the combination of regeneration and fibrosis which is the typical response following injury; the relative contribution of regeneration and fibrosis depends on the ability of the tissue to regenerate and the extent of the injury; the term fibrosis (scarring) refers to the deposition of collagen which occurs in repair, and fibrosis is the predominant healing process that occurs when the extracellular matrix (ECM) framework is damaged by severe injury.

Question 131

Based on proliferative activity, list the three types of tissues in the human body.

Answer 131

Continuously dividing (labile tissues): cells proliferate throughout life, replacing those that are destroyed (e.g. surface epithelia (skin, vagina, cervix, oral cavity, excretory duct epithelium, GI tract epithelium, endometrium, urinary tract epithelium), bone marrow and hematopoietic tissues); in most of these tissues mature cells are derived from adult stem cells Quiescent (stable tissues): cells have a low level of replication, but can undergo rapid division in response to stimuli and thus have the capability of reconstituting the tissue of origin (e.g. liver, kidney, pancreas, smooth muscle, fibroblasts, vascular endothelial cells, osteocytes) Nondividing (permanent tissues): cells have left the cell cycle and cannot undergo mitotic division in postnatal life (e.g. neurons, skeletal muscle (some limited regenerative capacity), cardiac muscle)

Question 132

Explain the goal of stem cell therapy.

Answer 132

The goal of stem cell therapy is to repopulate damaged organs of a patient or to correct a genetic defect, using the cells of the same patient to avoid immunologic rejection.

Question 133

List and describe the two main mechanisms by which cells are stimulated to replicate.

Answer 133

Replication of cells is stimulated by growth factors or by signaling from extracellular matrix components.

Question 134

List and describe the three modes of signaling mechanisms in cell growth.

Answer 134

Receptors lacking intrinsic tyrosine kinase activity: Ligands for these receptors include many cytokines (IL-2, IL-3) and other interleukins, interferons alpha, beta, gamma, erythropoietin, growth hormone, prolactin, and granulocyte colony-stimulating factors These receptors transmit signals to the nucleus by activating members of the JAK (Janus kinase) family of proteins, resulting in a cascade leading to gene transcription. G-protein-coupled receptors: Constitute the largest family of plasma membrane receptors. A large number of ligands signal through this type of receptor (chemokines, vasopressin, serotonin, histamine, epinephrine, norepinephrine, calcitonin, glucagon, parathyroid hormone, corticotropin, rhodopsin); many common pharmaceutical drugs also target these receptors! Steroid hormone receptors: - Generally located in the nucleus. - Ligands diffuse through the cell membrane and into the nucleus, binding to and activating the receptor. - Activated receptors then bind to specific DNA sequences known as hormone response elements within target genes, or they can bind to other transcription factors. - Ligands using this pathway are steroid hormones, thyroid hormone, vitamin D, and retinoids. - A group of nuclear receptors belonging to this class of receptors are called peroxisome proliferator-activated receptors, involved in a broad range of responses including adipogenesis, inflammation, and atherosclerosis.

Question 135

List and describe the four types of receptors involved in signaling induction pathways.

Answer 135

?

Question 136

State the growth factor most important for fibrosis, and the growth factor most important for angiogenesis.

Answer 136

Transforming Growth Factor Beta (TGF-Beta) - Has a great number of effects (pleiotropic). - TGF-Beta inhibits the growth of most epithelial cells; acts as a potent fibrogenic agent (causes fibrosis); has a strong anti-inflammatory effect but may enhance some immune functions. - TFG-Beta is implicated in the development of fibrosis in a variety of chronic inflammatory conditions, especially in the lungs, kidney, and liver; also implicated in hypertrophic scars and systemic sclerosis, Marfan syndrome. Vascular Endothelial Growth Factor (VEGF): - VEGFs are a family of proteins that induce blood vessel formation in development (vasculogenesis) and promote growth of new blood vessels (angiogenesis) in adults in chronic inflammation, healing of wounds, and tumors. - VEGFs signal by binding to VEGFRs (VEGFR-1,2,3). - VEGF-C and VEGF-D bind to VEGFR-3 and act on lymphatic endothelial cells to induce the production of lymphatic vessels (lymphangiogenesis).

Question 137

List and describe the functions of the ECM, as well as the two forms of the ECM.

Answer 137

Tissue repair and regeneration is dependant not only on the activity of soluble factors such as growth factors but also on interactions between the cell and the components of the extracellular matrix (ECM). The ECM regulates the growth, proliferation, movement, and differentiation of the cells that live within it, and is continuously being remodeled. The functions of the ECM include: - Mechanical support. - Control of cell growth. - Maintenance of cell differentiation. - Scaffolding for tissue renewal: regeneration of a tissue will result in restitution of the normal structure only if the ECM is not damaged; disruption of the ECM leads to collagen deposition and scar formation. - Establishment of tissue microenvironments (e.g. basement membranes) - Storage and presentation of regulatory molecules. Interstitial matrix: found in spaces between epithelial, endothelial, and smooth muscle cells, as well as in connective tissue; consists mostly of fibrillar and nonfibrillar collagen, elastin, fibronectin, proteoglycans, and hyaluronan. Basement membranes: associated with cell surfaces, and consist of nonfibrillar collagen (mostly type IV), laminin, heparin sulfate, and proteoglycans.

Question 138

List and describe the key steps of repair by tissue collagen deposition.

Answer 138

Formation of a blood clot: The blood clot stops bleeding and serves as a scaffolding for migrating cells, attracted by growth factors, cytokines, and chemokines. Within 24 hours neutrophils appear and release proteolytic enzymes to clean out debris and invading bacteria. Formation of granulation tissue: Fibroblasts and endothelial cells proliferate in the first 24 to 72 hours to form granulation tissue, which is mesenchymal tissue containing proliferating fibroblasts and new small blood vessels (angiogenesis). The small blood vessels are leaky, resulting in localized edema within the extravascular space. The amount of granulation tissue formed is dependant on the size of the tissue deficit and the intensity of the inflammation (more granulation tissue formed in healing by secondary intention) Cell proliferation and collagen deposition: Neutrophils are largely replaced by macrophages after 48-96 hours. Macrophages are a key cellular constituent of tissue repair, clearing extracellular debris, fibrin, and other foreign material at the site of repair, and promoting angiogenesis and ECM deposition. Migration of fibroblasts to the site of injury is driven by chemokines, TNF, PDGF, TGF-Beta, and FGF. Fibroblast proliferation is driven by multiple growth factors (PDGF, EGF, TGF-Beta, FGF, and cytokines IL-2 and TNF). Macrophages are the main source for these factors, although other inflammatory cells and platelets also produce them. In 24-48 hours, epithelial cells move from the wound edge, depositing basement membrane material as they move. Collagen fibrils become more abundant, with TGF-Beta serving as the most important fibrogenic agent. Scar formation: By the second week, the leukocyte infiltrate, edema, and increased vascularity largely disappear. By one month, a connective tissue scar is present, devoid of inflammatory infiltrates, and covered by an intact epidermis. Wound contraction: Wound contraction is the next event, mediated by myofibroblasts located at the edge of the wound that express smooth muscle alpha-actin and vimentin. This occurs in large wounds, and helps to close the wound. Connective tissue remodeling: Replacement of the granulation tissue by fibrous tissue (scar) involves changes in the composition of the ECM. The balance of ECM synthesis and degradation results in remodeling of the connective tissue framework. Some of the growth factors that stimulate synthesis of collagen and ECM tissue molecules also modulate the synthesis and activation of metalloproteinases, enzymes that can degrade these ECM components. Recovery of tensile strength: Net collagen accumulation depends on increased collagen synthesis as well as decreased collagen degradation. After the first week, wound strength of an incisional wound is only 10% that of normal skin; after 3 months or so, wound strength reaches a plateau of about 70-80% of the tensile strength of unwounded skin. Tensile strength results from collagen deposition as well as from structural modification of the collagen (cross linking, increased fiber size).

Question 139

Describe the three stages of wound healing.

Answer 139

Inflammation - clot formation - chemotaxis Proliferation - re-epitheliaization - angiogenesis and granulation tissue - provisional matrix Maturation - collagen matrix - wound contraction

Question 140

List the systemic and local factors that influence wound healing.

Answer 140

systemic factors: Nutrition: protein deficiency, deficiency in vitamin C impair healing Metabolic status (e.g. diabetes associated microangiopathy impairs healing) Circulatory status (e.g. impaired blood supply due to arteriosclerosis or venous abnormalities impairs healing) Hormones such as glucocorticoids have anti-inflammatory effects that influence the inflammatory response, as well as inhibit collagen synthesis, resulting in impaired healing in acute wounds local factors: Infection (most important factor), delays healing Mechanical factors can delay healing Foreign bodies can delay healing Size, location, and type of wound: wounds in richly vascularized areas heal faster than those in poorly vascularized areas. Small incisional wounds heal faster and with less scar formation than large excisional wounds or wounds caused by blunt trauma.

Question 141

Please note that the last slide prior to the discussion of laboratory testing is quite important, and make sure that you can explain its key points!

Answer 141

know this

Question 142

Define accuracy, precision, prevalence, sensitivity, specificity, and predictive value of both positive and negative tests. Explain the effect of prevalence on the predictive value of a positive test.

Answer 142

Accuracy: ability of the test to actually measure what it claims to measure correctly. Precision: ability of the test to reproduce the same result when repeated. Sensitivity is the probability that an individual with the disease will test positive. It is the number of patients with a positive test who have the disease (true positives) divided by all the patients who have the disease. A test with high sensitivity will not miss many patients who have the disease (low false negative rate). Specificity is the probability that an individual without the disease will test negative. It is the number of patients who have a negative test and do not have the disease (true negatives) divided by the number of patients who do not have the disease. A test with high specificity will infrequently identify patients as having a disease when they do not (low false positive rate). Positive predictive value (PPV) refers to the probability that a positive test correctly identifies an individual who actually has the disease. It is calculated from the true positives divided by all who test positive for the disease. Negative predictive value (NPV) refers to the probability that a negative test correctly identifies an individual who does not have the disease. It is calculated from the true negatives divided by all who test negative for the disease. Unlike sensitivity and specificity, PPV and NPV are affected by the prevalence of a disease (prevalence is defined as the percent of individuals with the disease in the population being tested). Disease prevalence is the key factor in determining the utility of a test, and the usefulness of a positive test decreases as disease prevalence decreases.

Question 143

marfan syndrome

Answer 143

Patients with Marfan syndrome have an inherited defect of fibrillin, resulting in abnormal elastic fibers, manifested by changes in the cardiovascular system (aortic dissection) and the skeleton

Question 144

Describe the substrates, products, and key enzymes of prostaglandin synthesis

Answer 144

substrates: arachidonic acid from the diet (in a pinch, it can be synthesized from linoleic or linolenic acids, which are also from the diet. This requires energy) see slide 16 still trying to work out all the details on this one

Question 145

. Describe how prostaglandins mediate vasodilation and platelet aggregation in normal physiology and in wound response.

Answer 145

Healthy vascular endothelial cells release PGI2, which prevents platelet clotting and keeps blood vessels open (vasodilation). Damage to tissues results in a proteolytic cascade and calcium release which culminates in thrombin activation. Thrombin is a protease which cleaves soluble fibronogen to form fibrin, which polymerizes into a wound covering matrix. When platelets contact thrombin, they release thromboxane A2 (TXA2), which acts as a paracrine and autocrine hormone to induce platelet aggregation and other wound responses.

Question 146

Describe the different functions of sugar modifications to proteins, lipids and other sugars (e.g. to make lactose)

Answer 146

Most glycoproteins are secreted, and act as hormones, antibodies, enzymes, extracellular matrix proteins, or mucus. Some glycoproteins serve as receptors on the cell surface, e.g. antibodies. Some glycoproteins are lysosomal proteins that function to degrade material that a cell has endocytosed. Glycolipids are lipids that sit in the membrane with their sugar moieties facing outward. They can serve as antigens, recogition motifs, and receptors. Glycoproteins are sugar modified proteins. They can either be secreted to the blood or extracellular matrix, sit in a cell’s plasma membrane, or exist in the lysosome. Proteoglycans are proteins with extensive glycosylation. Proteoglycans are an important part of the extracellular matrix and tissues such as cartilage.

Question 147

eicosanoids overview

Answer 147

Prostaglandins: Synthesized by all cell types They function as autocrine and paracrine hormones and have a very short half life They are induced by a broad range of stimuli and mediate a broad range of biological responses. Thromboxanes: Synthesized from prostaglandin, most importantly in platelets Mediate vasoconstriction, platelet aggregation

Question 148

aspirin

Answer 148

Its activities against COX-2 explain aspirin’s desirable effects: anti-inflammatory pain relief fever reduction Its activities against COX-1 explain aspirin’s undesirable side effects: stomach ulcers permanently takes out cyclooxygenase

Question 149

ibuprofin

Answer 149

inhibits both Coxs, but not permanently

Question 150

acetominofin

Answer 150

inhibits both Coxs, but not permanently

Question 151

naproxin

Answer 151

inhibits both Coxs, but not permanently

Question 152

anything ending in -coxib

Answer 152

inhibits only cox-2, but increased risk of stroke/heart attack

Question 153

corticosteroids (anything ending in -sone)

Answer 153

Corticosteroids such as hydroxycortisone, prednisone, and dexamethasone interfere with phospholipase 2 and cyclooxygenase. This prevents inflammation by blocking the production of both leukotrienes and prostaglandins. Systemic corticosteroids can be gluconeogenic: Increase muscle protein breakdown Increase PEP-CK synthesis Patients treated with high doses of corticosteroids may develop hyperglycemia. Inhaled steroids can be used for the treatment of asthma, and have fewer side effects than systemic treatment.

Question 154

drugs that end in -lukast

Answer 154

Leukotrienes are important in asthma, and are a new drug target: Leukotrienes are released by mast cells in response to a (real or perceived) allergen. Leukotrienes cause bronchoconstriction. Cys-leukotrienes act as chemoattractants for eosinophils, and cause eosinophil infiltration into the airways. Drugs which block the CysLT1 receptor can be used in the long term management of asthma; they are not suited for acute asthma attacks. montelukast (Singulair) zafirlukast (Accolate)

Question 155

jaundice

Answer 155

Neonatal jaundice occurs immediately after birth due to an increase in hemolysis and an immature glucuronate conjugating system. Hemolytic jaundice can occur if there is excessive red blood cell destruction. Hepatocellular jaundice can occur if the liver is not functioning, e.g. due to damage from excessive alcohol consumption. Obstructive jaundice is caused by a disturbance in bile drainage, due to a gallstones or a tumor, e.g.

Question 156

Tay-Sachs disease

Answer 156

characterized by early onset mental retardation and motor impairment. It is caused by ganglioside accumulation in neuronal cells. By 18 months of age, most Tay-Sachs patients are blind, deaf and spastic. Most die by 3 years of age. Tay Sachs is an autosomal recessive disease most common in Ashkenazi Jews. 1 in 28 carry the defective gene. The defective gene is in the α subunit of hexosaminidase. This produces a defective hexosamindase A, the trimer of 1 α and 2 β subunits, which cleaves the N-acetyl-D-galactose bond in gangliosides. Hexosaminidase B is still active.

Question 157

Sandhoff disease

Answer 157

similar to Tay-Sachs, but with an earlier onset. It is characterized by ganglioside and globoside accumulation in neuronal cells. The defective gene is the β subunit of hexosamindase. This affects the activities of both hexosaminidase A and B, reducing the ability to degrade gangliosides and globosides in lysosomes.

Question 158

Gaucher disease

Answer 158

an autosomal recessive defect in β-glucosidase. The defect results in accumulation of glucocerebreside in brain, liver, bone marrow, and the spleen. Gaucher disease can be treated effectively with infusions of recombinant β-glucosidase (Imiglucerase).

Question 159

Fabry disease

Answer 159

an X linked lysosomal disorder. It is caused by a deficiency of α-galactocerebrosidase A (a.k.a. α-galactosidase). It is characterized by progressive renal, cardiovascular and cerebrovascular failure caused by accumulation of glucose – galactose – galactose globosides. Like Gaucher’s disease, Fabry disease can be treated with enzyme replacement therapy (Agalsidase).

Question 160

Interleukins (IL)

Answer 160

group of cytokines (signaling molecules) expressed by WBC (leukocytes)

Question 161

Early response to pathogens

Answer 161

``` - trigger innate response: o flush (fluid extravasation) o clot (trap particles) o remove (Neutrophils and Macrophage) - complement decorates cells and triggers phagocytosis ```

Question 162

Mast cells

Answer 162

are sentinels (important) - Mast cells – start inflammatory response - Mast cell coordinates the inflammatory response by three mechanisms: o direct: TLR o Fc-recepter mediated: Fc receptor o complement-receptor mediated: CR - Recognition by TLR; Fc; CR - responds by IL1/TNF/IL-6 o stimulates acute phase response

Question 163

Neutrophil Extravasation

Answer 163

- CXCL8 – recruits neutrophils o chemokine - Neutrophils are continuously contacting the endothelia lining (Marginalization) - at sites of inflammation the region expresses additional adhesion molecules (integrins) - Neutrophil receives the CXCL8 message to diapedese - Neutrophil will follow the chemokine gradient to target the inflammatory site

Question 164

Macrophage direct response

Answer 164

- IL-12 – activates NK cells o induces differentiation of CD4 T cells into Th1 cells - CXCL8 – recruits neutrophils - IL-6 – lymphocyte activation o increased antibody production - TNF-a – increased vascular permeability

Question 165

Acute Phase Response

Answer 165

- bacteria induce macrophages to produce IL-6 | o acts on hepatocytes to induce synthesis of acute-phase proteins

Question 166

Inflammatory response

Answer 166

- Vasodilation o increased blood flow - Increased vascular permeability o plasma infusion - Emigration of neutrophils o Extravasation

Question 167

Adaptive Immunity

Answer 167

- Capable of virtually recognizing any molecular structure greater then 100 Da - Highly efficient clearance - Anticipatory - Memory - Gene recombination - Somatic hypermutation

Question 168

Primary Lymphoid Organs

Answer 168

- Location of the niche that houses Lymphoid Progenitor cells - Formation of the functional lymphocyte o Positive Selection, antigen receptor activation  manufacture receptors and put on surface  functional in sense that it recognizes and responds o Negative Selection, removal of cells recognizing self tissue o only about 1% survive positive and negative selection - Only T-cells can last a lifetime Bone Marrow Thymus Fetal Liver

Question 169

Bone marrow

Answer 169

site of hematopoiesis lymphoid progenitor cells mature b cells (b2)

Question 170

thymus

Answer 170

mature b cells cd4 t cells (helper) cd8 t cells (cytotoxic) cd25 t cells (regulatory)

Question 171

fetal liver

Answer 171

"specialized immune cells" mast cells astrocytes (bllod brain barrier)

Question 172

Secondary Immune Organs

Answer 172

- Site for lymphocyte education - Naïve T cells and mature B cells are match to antigen - Site of the Germinal Center - T cells differentiate into effector cells - B cells differentiate into plasma and memory cells - Organs: o Lymph Node – drainage from tissue o Peyer’s Patch – lining of GI tract o Spleen – only things occurring in circulation o Vermiform Appendix o Tonsils

Question 173

Dendritic Cell report process

Answer 173

``` - DC take up debris o Phagocytosis - DC identifies non-self o TLRs  - DC “matures” o Expresses CCR7 - DC is recruited to node o Follows CCL19 (chemokine DC follows to lymph node) ```

Question 174

Dendritic Cells

Answer 174

- Dendritic cell matures when exposed to a PAMP - immature DC roams through the tissues constantly sampling material o packing/repacking MHC class II - PAMP stimulate a change: o new chemotactic pattern to seek the lymph node o DC change shape (round to stellate) o Express high amounts of MHC class II for T cells to sample o Express co-stimulatory molecules (CD80/CD86) - Only dendritic cell can activate a naïve T cell

Question 175

Lymphocyte Activation

Answer 175

- DC also provides a signal to control early T cell development o IL-12 – directs development of Th1 o IL2 autocrine factor – induces proliferation

Question 176

Entry Into and Out of the Node

Answer 176

- Naïve T cells and Mature B cells enter the node - Naïve T cells express a selectin (CD62L) that permits entry o effector cells don’t have CD62L, so they cannot get into the lymph node - In the presences of a mature DC the T cell is activated (begins producing IL-2) o begins in the paracortical area - T cells start to proliferate and begin differentiating into Th1, Th2 or Th17 - Follicular dendritic cells decorated with surface antigen from the inflammatory site begin attracting B cells - B cells refine Ag affinity by somatic hypermutation, and direct function through class switching

Question 177

Germinal Center

Answer 177

- B-cell selection is controlled by the availability of antigen bound to the surface of the Follicular dendritic cell - T cells collect to the area based on the MHC class II expression on the B cells - B cells go through a continuous change in antigen receptor binding affinity due to somatic hypermutation - B-cells remain in the GC only as long as their surface Ig’s continue to bind antigen on the FDC - T cells only remain in the region as along as the B cells are present and presenting appropriate Antigen on their MHC class II

Question 178

B Cell

Answer 178

- Produce antibodies (secretory and surface) - Mature B cells emerges from the bone marrow - Visits Secondary Immune organs - Screens antigen on the surface of follicular dendritic cells - Antigen matched cells differentiate in Germinal Centers - Plasma Cells emerge and returns to the bone marrow - Resting Mature B cell (B-2 type) expresses IgM and IgD o once exposed to antigen the IgD is losed - IgM is the product of gene recombinations - Isotype switching (IgG, IgA, IgE) does occur to additional recombinations - Further changes to the antigen binding region are due to somatic hypermutation