Chapter 8 - Immune System Flashcards
What do superantigens do?
(Proteins) cause the immune system to become nonspecifically over activated.
Leaves the body open to SUPERINFECTION (infection with other pathogens)
Innate versus adaptive immunity
Innate: defenses that are always present, non-specific
Adaptive: target a specific pathogen, specific. SLOWER but can mount a faster attack in subsequent infections
What are B-cells?
Where are they produces?
Where do they mature?
Produced in the bone marrow (leave bone marrow mature but naive)
Stored and activated in the SPLEEN
B cells turn into plasma cells to produce antibodies as part of adaptive immunity. Dissolve and act in the blood –> HUMORAL immunity
What are T-cells?
Where are they produced?
Where do they mature?
Produced in the bone marrow (immature)
Mature in the THYMUS, a small gland in front of the pericardium
The main agent of CELL-MEDIATED immunity because they coordinate the immune system and directly kill infected cells
What do lymph nodes do?
Filter lymph. Provide a place for immune cells to communicate and mount an attack.
B-calls can be activated in the LN as well
What is gut-associated lymphoid tissue?
Immune tissue located in proximity to the digestive system, which is a site of potential invasion by pathogens.
Includes: Tonsils Adenoids Peyer's patches (small intestine) Lymphoid aggregates (appendix)
What happens in the spleen?
Storage for blood (good for use in case of hemorrhagic shock)
Filter for blood and lymph
Recycle iron
Site where immune responses can be mounted
What is hematopoiesis? Where does it take place?
The production of leukocytes (and red blood cells and platelets)
Takes place in the bone marrow
Hematopoietic stem cells gives rise to both granulocytes and agranulocytes
What do granulocytes have that agranulocytes don’t?
Granules in the cytoplasm
These contain toxic enzymes and chemicals that can be release via exocytosis
What are three types of granulocytes?
Neutrophils
Eosinophils
Basophils
What are some agranulocytes?
What does each do?
Lymphocytes Antibody production Immune system modulation Targeted killing of infected cells Monocytes Phagocytic cells in the blood Macrophages Monocytes when in tissue! ->Microglia in CNS ->Langerhan's cells in skin ->osteoclasts in bone
What is a complete blood count (CBC)?
What does high # of neutrophils mean?
What does high # if eosinophils mean?
CBC is a blood test that counts the number of red blood cells, platelets, and white blood cells.
When ordered WITH A DIFFERENTIAL each type of blood cell is counted.
90% neutrophil means maybe bacterial infection (normally 40-80%)
20% eosinophils might mean parasitic infection (normally 1-6%)
What are defensins?
What other secretion from this organ?
An antibacterial enzyme found on the skin
Sweat is anti microbial
What are lines of defense in the respiratory system?
2
Cilia and mucus (cilia push particles up the oropharynx; mucus traps particles)
What is lysozyme?
A nonspecific antibacterial enzyme
Secreted in tears and saliva
Innate immunity in the GI tract
2 ways
Stomach secretes ACIDS (kills most pathogens)
Gut is COLONIZED by bacteria already (potential invaders can’t compete)
What is complement?
What are the two pathways?
Consists of proteins in the blood that can have a nonspecific defense AGAINST BACTERIA
Complement proteins punch a hole in bacterial cell wall, makes them osmotically unstable.
Classical pathway (binding of antibody to a pathogen) Alternate pathway (doesn't require antibody)
What are interferons?
Protein that prevents viral replication and dispersion.
Produced by cells that have been infected with VIRUSES.
Makes nearby cells less permeable: harder for virus to infect them, and has them reduce production of proteins (both viral and cellular)
Upregulate MHC class 1 and 2, aka increased antigen presentation and better detection of infected cells.
INTERFERONS = flu-like symptoms of viral infection
What 3 things does an activated macrophage do?
- Phagocytizes the invader via endocytosis (eats it)
- Digests the invader using enzymes
- Presents little pieces (mostly peptides - aka antigen) using MHC
What do MHC molecules do?
Bind with the antigen and carries it to the cell surface
By holding out the antigen, the cells of the ADAPTIVE immune system can recognize it and act accordingly.
MHC class 1 versus MHC class 2
MHC class 1:
All nucleated cells
Can present any protein, but useful to detect presence of pathogen (because then unfamiliar protein is presented)
ENDOGENOUS PATHWAY - antigen comes from inside the cell
MHC class 2:
Antigen-presenting cells
(macrophages, dendritic cells, some b-cells, some activated epithelial cells)
EXOGENOUS PATHWAY - bc the antigens originated outside the cell
What is a pattern recognition receptor?
Toll-like receptors
Macrophages and dendritic cells have them
Can recognize the category (bacteria, virus, etc) of the invader and recruit the right immune cells.
What is a natural killer cell?
A nonspecific lymphocyte
Detect the downregulation of MHC
Induce apoptosis
*eg: cancer cells down regulate MHC expression
What is a neutrophil?
Most populous, short-lived (5 days)
Phagocytes that target BACTERIA (like macrophages)
Track bacteria using Chemotaxis
Can also detect bacteria once they have been opsonized
Pus = dead neutrophils
What does it mean when an invader is opsonized?
It means that it has been marked with an antibody from a B-cell
(Antibody in the blood binds to the antigen, and attracts leukocytes to phagocytize it)
What is an eosinophil?
Red-orange granules
Involved in allergic reactions and parasites
Releases large amounts of HISTAMINE (an inflammatory mediator)
Release of histamine results in blood vessel dilation and increased leakiness of blood vessels
What is a basophil?
Large purple granules
Least populous
Involved in allergic responses
Also releases HISTAMINE and initiates inflammation
What is a mast cell?
Similar to basophil
Smaller granules
Exist in tissues, mucosa, and epithelium
What is humoral immunity?
Involves B cells
Involves the production of ANTIBODIES
May take up to a week to become fully effective
Antibodies are produced by by the B cells
Tell me about antibodies
Where are they found (3)
What do they do?
Aka immunoglobulins
They can be found on the surface of cells or can float freely in blood/chyle/air
Free floating antibodies:
1. Opsonization
(attach to antigen and attract leukocytes)
2. Agglutinate
(cause pathogen to clump together to be phagocytized)
3. Neutralize (block pathogens ability to invade tissue)
For cell surface antibodies:
- Pathogen bind to b-cell to activate it
- Formation of plasma and memory cells
For mast-cell antibodies:
1. Degranulation
(Exocytosis of granules, incl histamine, causing inflammatory allergic reaction)
What is the molecular composition if antibodies?
Y-shaped molecule
2 identical heavy chains
2 identical light chains
Held together by disulfide linkages and noncovalent interactions
What is the antigen-binding region?
What does it have to do with immunity?
What is clonal selection?
The tips of the Y
Specific polypeptide sequences that will bind ONE specific antigen sequence.
The reason humoral immunity takes so long is bc the b-cell undergoes HYPERMUTATION of the antigen-binding region, trying to find the best match for the antigen.
The cells that can’t bind with high enough affinity will die - those that survive generate specificity. This is called CLONAL SELECTION
What is the “constant region/domain” of the antibody?
The region that doesn’t change (the stem of the Y).
Can initiate complement cascade
Natural killer cells, macrophages, monocytes, and eosinophils have receptors for this area
How many isotopes of antobodies are there?
FIVE
Each B-cell can only make one type of antibody (but many B-cells = many antibodies).
Different isotopes can be used at different times during the ADAPTIVE immune response: for diff pathogens, in diff areas of the body, etc.
What is isotype switching?
B-cells can change which isotope of antibody they produce when stimulated by certain cytokines (small proteins in cell signaling)
Where do naive b-cells wait when not activated?
In the lymph nodes
Wait for the correct antigen
When activated, what two cells does a B-cell produce?
PLASMA CELL
Produces a large amount of antibodies
Will die eventually
MEMORY CELL
Stay in the lymph node and await re-exposure to the same antigen.
Will love the lifetime of the organism
What is the primary response?
How long does it take?
Primary response is the activation of the B-cell by an antigen and the production of a plasma cell and a memory cell.
Takes 7 to 10 days.
What is the secondary response?
How long does it take?
The secondary response is when the memory cell is exposed to the antigen a second time.
More RAPID and ROBUST response.
*vaccinations and developed based on this
What type of bacteria can cause necrotizing fasciitis?
Group A streptococcus
Clostridium perfringens
Methicillin-resistant staphylococcus aureus (MRSA)
What are the 5 types of infectious pathogens?
Bacteria Viruses Fungi Parasites Prions
Typical bacterial (extra cellular infection). WHAT HAPPENS?
- Macrophages - engulf bacteria and release inflammatory mediators
- Macrophages DIGEST the bacteria and PRESENT the pieces on the cell surface - MHC-2.
- Inflammatory cells arrive (neutrophils and more macrophages)
- Mast cells are activated by the inflammation and degranulate
- Histamine is released
- Leakiness if capillaries increases
- Immune cells can flood the tissue more easily from the bloodstream
- Dendritic cell goes to LN and presents antigen to B-cells
- B-cells make antibody, and plasma/memory cell
- Antibodies travel through bloodstream to infected area, where they tag bacteria for destruction
- Dendritic cells also present to T-cells in the thymus, particularly CD4+
- T-helper 1 and T-helper 2 activate macrophages and activate B-cells.
- Memory B- and T-cells
Typical viral (intracellular infection). WHAT HAPPENS?
- Virally infected cell makes interferons, reducing permeability of nearby cells, malaise, etc
- Cell presents viral proteins on cell surface with MHC-1
- CD8+ cells recognize cell and inject toxins into it –> apoptosis
- If virus has impaired MHC-1 production, NK cells recognize this and cause apoptosis
- Memory T-cells
What are t-helper 1 and t-helper 2?
T(h)1:
Release interferon gamma which activates macrophages and increases their ability to kill bacteria.
T(h)2:
Help activate B-cells
What are self-antigens?
The proteins and carbohydrates that are normally present on the surface if every cell of the body.
What is autoimmunity?
Examples of autoimmune disorder
When the immune system fails to differentiate between SELF and FOREIGN.
Type 1 diabetes: body attacks B-cells in islets of Langerhan.
RA, MS, psoriasis, lupus, Graves’ disease, Guillain-barré syndrome
What is a allergic reaction?
When the immune system thinks that an antigen is dangerous when it is not. (Immune system becomes overactivated)
Example: pet dander, peanuts, pollen.
What are hypersensitive reactions?
A family of immune disorders that include AUTOIMMUNITY and ALLERGIES.
What is active immunity?
Exposure to an antigen
(Naturally or artificially)
B-cells are activated and produce antibodies (and memory cells)
In vaccines: the antigen is a weakened or killed form of the microbe, or part of the microbe’s protein structure.
What is passive immunity?
Transfer of antibodies
Only the antibody, not the plasma cells, are given to the individual.
Ex:
Transfer of antibodies across the placenta
Sometimes after exposure to tetanus or rabies, some immunoglobulin is given to prevent pathogen from spreading.
What is Guillain-Barré syndrome?
An autoimmune disease where the myelin of peripheral nerves is attacked
Rare cases sometimes result from immunization (as well as encephalitis - brain inflammation)
What are the vessels of the lymphatic system like?
One way vessels
Vessels get larger as they move towards centre of the body
Carry lymph
What is the thoracic duct?
In the posterior chest
Delivers fluid into the left subclavian vein (near the heart)
What is the lymph node’s structure?
Lymphatic channel
An artery
A vein
Main roles of the lymphatic system:
3
- Equalization of fluid distribution
- Transportation of biomolecules
- Immunity
How much fluid leaves the capillaries and enters the tissues depends on what TWO things?
How does this create extra fluid?
Hydrostatic pressure
Oncotic pressure
(Starling forces)
Extra fluid results because the net pressure drawing fluid in at the venule end is slightly lower than the pressure that pushed the fluid out at the arteriole end.
What happens if oncotic pressure decreases?
When might this happen?
Less fluid will go back into the venule (more liquid will be left in the tissues)
Ex: low concentration of albumin (a key plasma protein)
When does edema occur?
When the lymphatic vessels are overwhelmed
Edema: swelling due to fluid in tissue.
What biomolecules does the lymphatic system transport?
Fats from the digestive system into the bloodstream
What are LACTEALS?
Small lymphatic vessels located at the centre of each villus in the small intestine.
Fats are packaged into chylomicrons by intestinal mucosal cells, enter the lacteal for transport.
What is chyle?
Lymphatic fluid, carrying many chylomicrons.
Has a milky white appearance.
