Intro to Immunity

Question 1

Antigens

Answer 1

biochemical components (proteins, carbohydrates, lipids, and nucleic acids) that alert leukocytes to their presence within the body. Leukocytes recognize antigens via antigen receptors displayed on the leukocyte surface

Question 2

When a leukocyte binds to an antigen via its antigen receptor, the interaction induces the leukocyte to eliminatevantigen by one or more mechanisms:

Answer 2

phagocytosis, cytotoxicity, synthesis of soluble factors

Question 3

Phagocytosis

Answer 3

ingestion and enzymatic digestion of particulate antigens, e.g.,microbes, allergens, damaged host cells, etc.

Question 4

Cytotoxicity

Answer 4

induction of lysis and/or apoptosis of microbe-infected host cells, tumor cells, or mismatched tissue grafts

Question 5

Synthesis of soluble factors

Answer 5

production of antibodies, complement components, defensins, cytokines, and other substances that help eliminate the foreign antigen

Question 6

How do immunologists separate the immune system?

Answer 6

Innate versus adaptive immunity

Humoral versus cell-mediated immunity

Question 7

Innate immunity

Answer 7

includes all host defenses that are present and functional at birth, including natural barriers like skin, and leukocytes whose antigen receptors have broad specificity, e.g., phagocytes, granulocytes, NK cells. Complement/CRP/defensins/cytokines, pattern rec receptors, normal flora

broadly identifies groups of antigens, rapid response, no memory, unaffected by vaccination

Question 8

Adaptive immunity

Answer 8

develops slowly in response to host contact with a specific antigen and includes just four major components: antibodies, B lymphocytes, plasma cells, and T lymphocytes.

very specific, slow response, memory, improved by vaccination

Question 9

Immunological memory/Clonal Selection Theory

Answer 9

the increase in speed and strength with which B and T lymphocytes respond to an antigen upon re-exposure to that same antigen. Immunological memory can be explained by the Clonal Selection Theory, which states that a given antigen will induce proliferation and differentiation only of those B and T lymphocytes that have receptors specific for that antigen. Some of the responding B and T lymphocytes will develop into memory cellsthat can survive for years within the lymph nodes. Memory cells undergo rapid activation and expansion when they encounter the same antigen againat a later time, resulting in greater numbers of antigen-specific lymphocytes with higher affinity antigen receptors than in previous encounters.

Question 10

Humoral immunity

Answer 10

mediated by soluble proteins and glycoproteins present in serum and the extracellular tissue fluids. It is most effective against extracellular pathogens rather than pathogens that live inside host cells

Question 11

Cell-mediated immunity(CMI)

Answer 11

is mediated by “effector cells” that directly kill intracellular and extracellular pathogens, tumors, and damaged host cells by phagocytosis or cytotoxicity.

Question 12

The most important humoral immune factors are:

Answer 12

Antibodies (immunoglobulins)***–highly antigen-specific glycoproteins produced by B cells and plasma cells

Complement –a series of serum proteins that work together to lyse bacteria and other pathogens

C-reactive protein (CRP) –a general marker for inflammation or infection

Cytokines –soluble proteins that are used for communication between leukocytes

Question 13

The most important effector cells in CMI are:

Answer 13

Phagocytes that engulf and kill extracellular pathogens using enzymes and reactive oxygen species generated within the phagolysosome. The most efficient phagocytes are neutrophils and monocytes/macrophages.

Granulocytes that release enzymes and reactive oxygen species from granules to kill extracellular pathogens. The most efficient granulocytes are neutrophils, eosinophils, and basophils.

Cytotoxic cells that release enzymes and use receptors on their surfaces to induce apoptosis in infected host cells or tumors. The most important cytotoxic cells are natural killer cells (NK cells) and cytotoxic/cytolytic T cells (Tc cells).

Question 14

Antibody, complement component C3b, and CRP are opsonins. Opsonins are….

Answer 14

substances that coat bacteria and other particulate antigens to aid their recognition and ingestion by phagocytes. Many bacteria have capsules that protect them from phagocytosis. However, when the capsules become coated by opsonins, the capsules no longer provide protection against phagocytosis.

Question 15

Leukocytes

Answer 15

White blood cells that carry out the functions of the immune system. They develop by the process of hematopoiesis from self-renewing hematopoietic stem cells in the bone marrow.

Question 16

CD34 and Stem cell antigen-1 (SCA-1)

Answer 16

these markers are used clinically to enrich stem cells for transplantation and immune reconstitution

Question 17

The two major lineages of leukocytes arising from hematopoietic stem cells are

Answer 17

myeloid and lymphoid

Question 18

Lymphoid Cells

Answer 18

B lymphocytes

T lymphocytes

Natural killer (NK) cells

Question 19

Myeloid Cells

Answer 19

Erythrocytes –oxygen transport to tissues

Platelets (from megakaryocytes) –blood clotting and inflammation

Granulocytes (neutrophils, basophils, eosinophils)

Phagocytes (neutrophils, monocytes/macrophages)

Antigen-presenting cells (dendritic cells, monocyte lineage)

Question 20

Erythropoietin (EPO)

Answer 20

Reverse anemia (especially in renal failure) by restoring erythrocytes/RBCs

Question 21

Granulocyte colony-stimulating factor (G-CSF)

Filgrastim

Answer 21

Recovery of bone marrow (PMNs)

Question 22

Granulocyte-monocyte colony-stimulating factor (GM-CSF)

Sargomastim

Answer 22

Recovery of bone marrow (PMNs, monocytes, macrophages)

Question 23

IL-11

Oprelvekin

Answer 23

Reverse thrombocytopenia (platelets)

Question 24

Thrombopoietin

TPO

Answer 24

Reverse thrombocytopenia (platelets)

Question 25

Mucosa-associated lymphoid tissue (MALT; secondary lymphoid tissue)

Answer 25

The MALT responds primarily to antigens that enter the body through mucosal surfaces. B lymphocytes in the MALT produce mainly secretory IgA, an antibody class that resists digestive enzymes found in the gut and other mucosal tissues.

Question 26

Examples of MALT

Answer 26

- Gut-associated lymphoid tissues (GALT): lines intestinal tract - Bronchus-associated lymphoid tissue (BALT): lines respiratory tract - Genito-urinary tract-associated lymphoid tissue (GU-ALT) - Specific tissues include the lamina propria, tonsils, adenoids, appendix, and Peyer’s patches. Peyer’s patches are loose clusters of lymphoid tissue in the small intestine. M cellsare epithelial cells overlying Peyer’s patches specialized for transcytosis of antigens from the lumen to subepithelial T cells.

Question 27

White Pulp of spleen

Answer 27

comprises the lymphocyte-rich regions of the spleen. It contains: T cells arranged in a periarteriolar lymphoid sheath (PALS)around a central arteriole B cell-rich follicles(some containing germinal centers) occupying the space between the PALS and the marginal sinus A marginal zone at the outer boundary of the white pulp. The marginal zone contains specialized macrophages and additional B cells

Question 28

Red Pulp of Spleen

Answer 28

contains plasma cells, resident macrophages, erythrocytes, platelets, granulocytes and lymphocytes. Its main function is hemocatheresis, the destruction of aged platelets and erythrocytes. Iron recycled from erythrocytes is stored here.

Question 29

Spleen

Answer 29

responds primarily to blood-borne antigens. It is the major organ where antibodies are synthesized and released into circulation. Asplenic persons are highly susceptible to infection by encapsulated bacteria, e.g. Streptococcus pneumoniae, Haemophilus influenzae, Neisseria and Salmonella spp. This is because antibodies are needed as opsonins to neutralize the anti-phagocytic property of bacterial capsules. The spleen is located in the upper left quadrant of the abdomen.

Question 30

Medulla (of the lymph node)

Answer 30

Medullary cords contain closely packed lymphocytes and plasma cells Medullary sinuses contain macrophages Medullary sinuses communicate with the efferent lymphatics

Question 31

Paracortex of Lymph node (T cell area)

Answer 31

Lymphocytes in the blood enter the paracortex region of the lymph node through specialized post-capillary venules called high endothelial venules (HEVs) HEVs contain specialized cuboidal cells that express adhesion molecules in high density These adhesion molecules allow lymphocytes to bind tightly to the venule wall, and then extravasate from the venule to enter the node The paracortex becomes greatly enlarged during extreme cellular immune responses. The paracortex is poorly developed in DiGeorge syndrome because affected individuals produce no/few T cells

Question 32

Cortex of Lymph Node (B cell area)

Answer 32

Primary folliclesin the cortex contain naïve B cells that have never contacted antigen Secondary folliclesin the cortex contain germinal centerscomposed of B cells undergoing mitosis in response to antigen stimulation

Question 33

Lymph nodes (secondary lymphoid organs)

Answer 33

respond primarily to antigens entering through the skin and subcutaneous tissues. The functions of lymph nodes and the lymphatic system include: - Isolation of infectious agents and cellular debris from the body - Surveillance and filtration of the lymph by macrophages - Storage and activation of B and T cells - Antibody production by B cells - Maintenance of interstitial fluid pressure and volume by returning excess water and dissolved substances from the interstitial fluid to the circulation - many afferent vessels but only 1 efferent

Question 34

T cell education is the process by which

Answer 34

self-reactive T cells are eliminated and is essential for avoiding autoimmune diseases. T cell education takes place in the cortex and medulla of the thymus.

Question 35

Thymus (a primary lymphoid organ)

Answer 35

encapsulated organ that develops from the epithelium of the third and fourth pharyngeal (branchial) pouches. It is a bilobed structure that reaches its maximum size at puberty and then atrophies with age. THIS IS WHERE T CELL EDUCATION AKA REGULATION OCCURS

Question 36

DiGeorge Syndrome

Answer 36

Persons with a chromosome 22 deletion(22q11.2) are born with little or no thymus. These patients are highly susceptible to viral infections and cancer because they have few or no functional T cells.

Question 37

Process of T cell development

Answer 37

- cell produced in bone marrow - cell travels to thymus: called double-negative thymocytes (have no CD molecules) - cell in cortex develops both CD4 and CD8 becoming a double-positive thymocyte - cell in medulla loses expression of one CD and becomes single positive cell

Question 38

Primary Lymphoid Organs

Answer 38

bone marrow thymus

Question 39

Secondary Lymphoid Organs

Answer 39

spleen, lymph nodes, MALT

Question 40

Bone Marrow

Answer 40

where B cells begin expression of surface immunoglobulin molecules

Question 41

Megakaryocyte

Answer 41

large cell with a lobulated nucleus found in the bone marrow that gives rise to platelets (thrombocytes)

Question 42

Platelets/thrombocytes

Answer 42

are anucleate cells that promote blood clotting and inflammation. They bind to collagen exposed on damaged endothelial cells, forming microthrombi.

Question 43

complete blood count (CBC)

Answer 43

reveal whether a patient has a normal absolute number of circulating white blood cells (WBC). The typical range in adults is 4500-10,800 WBCs/mcL

Question 44

Leukocytosis

Answer 44

higher than normal WBC count indicates infection, inflammation, leukemia, or trauma

Question 45

Neutrophil

Answer 45

purple EC bacteria live 2-3 days in circulation die in tissues IgG receptors

Question 46

Eosinophil

Answer 46

red worms hypersensitivity, IgE

Question 47

Basophil

Answer 47

purple-black worms hypersensitivity, histamine, IgE

Question 48

Mast Cell

Answer 48

purple worms hypersensitivity, histamine, IgE

Question 49

List the polymorphonuclear Granulocytes

Answer 49

Neutrophil, Eosinophil, Basophil, Mast Cell

Question 50

Polymorphonuclear (PMN) granulocytes

Answer 50

short-lived cells that contain a multi-lobed nucleus and granules rich in enzymes (e.g.,lysozyme) and other substances (e.g.,lactoferrin) that are harmful to microorganisms. Granulocytes also produce reactive oxygen species.

Question 51

Dendritic cells

Answer 51

related to macrophages and are found under the epithelia and in most organs. In the skin, they are called Langerhans cells. Dendritic cells are the most efficient antigen-presenting cells (APCs). They are necessary for activating naïve T cells (T cells that have never before encountered antigen).

Question 52

Monocytes and macrophages (mononuclear phagocytes)

Answer 52

- Circulating monocytes develop into tissue-fixed macrophages - The reticuloendothelial system (RES) is a network of tissue-fixed macrophages that remove foreign substances from the bloodstream and lymph - 10-18 μm diameter, horseshoe-shaped nucleus, long-lived - Functions are phagocytosis, antigen processing, andantigen presentation

Question 53

``` Example of Monocytes/macrophages of the mononuclear lineage: Kuppfer Alveolar macros/dust cells Splenic macros Peritoneal Macros Microglial cells Osteoclasts Mesangial cells Synovial A cells ```

Answer 53

``` liver lung spleen peritoneal brain bones kidneys joints ```

Question 54

Phagocytosis

Answer 54

recptor ligand interaction initiated macro pseudopods engulf bacterium/form phagosome phagosome fuses with lysosome=phagolysosome lysozymes destroy PDG of bacterial cell wall and ROS damage pt and DNA end of bacteria

Question 55

Antigen processing

Answer 55

destruction of bacteria within a phagolysosome Peptides specific to the destroyed bacteria are paired up with MHC, transported to cell surface, and used for T cell (antigen) presentation. Now cell is called APC

Question 56

Natural killer (NK) cells

Answer 56

part of the innate immune system. eliminate infected host cells (especially virus-infected cells) and tumor cells, so they are very similar to Tc cells in this regard. NK cells work most efficiently when the CD16 molecules on the NK cell surface bind to IgG-coated target cells. This collaboration between NK cells and IgG is called antibody-dependent cell-mediated cytotoxicity (ADCC). (Also CD56)

Question 57

B lymphocytes

Answer 57

develop in the bone marrow of humans and the Bursa of Fabricius of birds. They can differentiate into short-lived plasma cells that secrete high quantities of antibodies (immunoglobulins) or into long-lived memory cells that express surface immunoglobulin (sIg). The main function of B cells is to mediate humoral immunity. The antibodies they produce can: Neutralize toxins and microorganisms Opsonize microbes for phagocytosis Activate complement, leading to microbe lysis

Question 58

T lymphocytes

Answer 58

mature in the thymus. The T cell receptor (TCR) for antigen binds mainly to protein antigens. A TCR-associated accessory molecule, CD3, mediates signal tranduction to the T cell nucleus, thus activating the cell after antigen engagement. Activated T cells secrete cytokines or become highly cytotoxic toward infected host cells or cancer cells. Helper T, Regulatory T, Cytotoxic T

Question 59

Helper T cell (TH)

Answer 59

all are CD4+ (also CD3) immunity by cytokine secretion TH1:works with macrophages, NK cells and Tc cells to promote cell-mediated immunity TH2:stimulates antibody production by B cells to promote immunity against worms and allergens TH17:aidsclearance of extracellular bacteria and fungi

Question 60

Regulatory T Cells (Treg)

Answer 60

all are CD4+, CD25+ (CD3) Regulates the functions of macrophages, NK cells, and other T cell subsets Helps prevent autoimmunity via cytokine secretion

Question 61

Cytotoxic T (Tc) cell

Answer 61

all are CD8+ (CD3) Kills infected (especially virus-infected) and neoplastic host cells (tumors) Involved in rejection of mis-matched tissue grafts

Question 62

B Lymphocyte (markers and function)

Answer 62

CD19, CD20, CD21(and surface immunoglobulin, sIg) antibody secretion - humoral immunity

Question 63

All T lymphocytes have what markers

Answer 63

CD3 and TCR