Section IV: Adaptive Immunity Flashcards
0
Q
What is specificity
A
- recognition of foreign substances
- a small molecule called hapten can also act as an antigen, but only when bound to a larger molecule
1
Q
What are the characteristics of adaptive immunity
A
- specificity
- self recognition
- memory
2
Q
What is memory
A
following the first exposure to antigen, immune system develops memory to provide rapid secondary response to same antigen
3
Q
What is the bodies two part strategy for eliminating foreign material
A
- humoral response
- cell mediated response
4
Q
What is a humoral response
A
eliminates antigens that are extracellular, for example bacteria in the bloodstream
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Q
What is a cell mediated response
A
deals with antigens residing within a host cell, for example a virus infected cell
6
Q
What is the structure of an antigen
A
large carrier molecule with epitopes projecting from surface. Epitopes interact with antibody and T cells
7
Q
What are the origins of exogenous antigens
A
those that have entered the body from the outside, for example by inhalation, ingestion, or injection
8
Q
What are the origins of endogenous antigens
A
those that have been generated within the cell, as a result of normal cell metabolism, or because of viral or intracellular bacterial infection
9
Q
What are superantigens
A
- do not behave as normal antigens. Rather than attaching to the MHC groove and triggering a normal immune response, superantigens attach onto the sides of the binding site
- as a result, T cells go on an unregulated rampage, uncontrollably releasing regulatory molecules-such as interferons- in toxic amounts
10
Q
What are Class I MHC’s
A
- presents proteins (antigens) from inside cell
- also presents abnormal proteins on surface of virus infected cells or tumor cells for inspection by cytotoxic T cells
- cytotoxic T cells will destroy “non-self” proteins
11
Q
What are Class II MHC
A
presents antigens from outside cell
-MHC II proteins display non-self which will be recognized by helper T cells
12
Q
Where are MHC II proteins found
A
ONLY on immune cells called antigen presenting cells
13
Q
What are activated dendritic cells
A
Found in those tissues which are in contact with the environment: in the skin and lining of nose, lungs, stomach, and intestines
14
Q
What are activated macrophages
A
- present antigen early in infection
- the presence of the antigen activates macrophages
- activated macrophage processes the antigenic material
15
Q
What happens following processing by an activated macrophage
A
- epitopes from the antigen are presented on the macrophage surface in combination with MHC proteins
- presented antigen is the recognized by helper T cells
- recognition activates the helper T cells
16
Q
What do activated helper T cells regulate
A
Cell mediated and Humoral immunity
17
Q
Does a T cell produce antibodies
A
no… never… never ever
18
Q
Do T cells interact with free antigens
A
no.
- anitgen must be presented to T cell by another cell (CD4 cell)
19
Q
Where are inactive (naive) T cells located
A
- restricted to circulation
- cannot migrate into tissues
20
Q
What is required for activation of T cells
A
- must encounter antigen presented on cell in antigen-MHC complex
- must also be concurrently stimulated by other molecules
21
Q
What does activation of T cells lead to
A
- formation of specific effector cells types
- effector T cells have different roles in cell mediated immunity
22
Q
What are functions of activated T cells
A
- proliferative, develop into different effector cells
- bring antigens to naive T cells
- Release lymphokines which act as messengers, they do not respond to specific antigen, instead lymphokines act to recruit other cell types, particularly macrophages
23
Q
What are CD4 T lymphocytes and what is there roll
A
- T cells that carry the CD4 marker can be T helper cells
- The role of T helper cells is to judge the significance of antigen presented by APC’s
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What happens following recognition by T helper cells
B cells development stimulated and other T cells by releasing cytokines
--impacts both cell mediated and humoral immunity
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What are Th1 cells
- judge antigen presented by macrophages. If a Th1 cell recognizes the antigen it responds by activating the macrophage
- Th1 cells orchestrate the cell mediated response by releasing lymphokines to stimulate proliferation of T cells, stimulate natural killer cells and recruit macrophages
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What are Th2 cells
- judge antigen presented by B cells
- if Th2 cell recognizes the antigen it responds by activating the B cell to produce antibody
- Th2 cells also stimulate proliferation of B cells
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What are T regulatory cells
also carry CD4 marker
| -block induction and activity of T helper cells and B cells
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What are CD8 T lymphocytes
Most T cells have the CD8 marker
- T cytotoxic cells induce apoptosis in self cells infected with virus or other microbe. Can also destroy cancerous cells
- >T cytotoxic cells recognize dysfunctional self cells by recognition of antigen presented on MHC I molecules
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What are T memory cells
long lived anitgen activated T cells that respond with heightened reactivity to secondary exposure with specific antigen
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How is Type IV hypersensitivity immune response mediated and how does it occur
mediated by cellular immunity
| -occurs when effector T cells regulate delayed allergic reactions
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What happens when CD4 and CD8 are out of balance
compromised cellular immunity
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What do lymphokines activate
activation of macrophages
- activation of polymorphonuclear leukocytes
- activation of lymphocytes
- other lymphokines
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What is macrophage activation factor (MAF)
activates macrophages and allows them to act as cytotoxic cells that non-specifically kill tumor cells
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What is Macrophage migration inhibitory factor (MIF)
- Inhibits random migration of macrophages, role in T cell activation
- MIF is now recognized as a principle cytokine modulating T cell/macrophage interactions in the expression of delayed hypersensitivity and acquired cellular immunity
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What are chemotactic factors
substances possessing chemotactic activity
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What is leukocyte inhibitory factor
inhibits the random and directed migration of polymorphonuclear leukocytes
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What is eosinophil stimulation factor
stimulates eosinophil migration and is produced by mitogen or specific Ag stimulation of spleen cells fro mice infected with Schistosoma mansoni
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What are interleukins
structurally and functionally distinct soluble proteins secreted by different types of leukocytes that are involved in cell to cell communication
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What are cytotoxic factors
term for a factor or an agent that has a specific destructive effect on cells
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What is growth inhibitory factor
found in normal human brain tissue and is expressed exclusively in the nervous system. GIF inhibits survival and the outgrowth of neurites in cortical neurons.
-Drastically reduced concentrations of this factors are found in the brains of patients with Alzheimer's disease
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What is osteoblastic factor
stimulates the formation of osteoblast cells in bone
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What is collagen production
factors stimulating formation of collagen
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What are interferons
proteins that elicit a virus non-specific antiviral activity. Also posses anti-proliferative and immunomodulating activities and influence the metabolism, growth and differentiation of cells in many different ways
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What is Transforming growth factor
- TGFs were identified initially as proteins secreted by virus-transformed mouse cells
- TGF-beta is the most potent known growth inhibitor for normal and transformed epithelial cells, endothelial cells, fibroblasts, neuronal cells, lymphoid cells and other hematopoietic cell types
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What does TGF-beta inhibit
proliferation of T lymphocytes
| -shuts down clonal expansion
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What mediates Humoral immunity
B lymphocytes
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What do B-cells do in response to antigens
proliferate and then differentiate into plasma cells which function to produce antibodies
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What are the characteristics of antibodies
- produced by plasma cells
- antibodies are found in blood serum
- antibodies also found on the surface of B lymphocytes
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Why are there antibodies found on B cells
allows B cell to interact with specific antigens
- antigen interaction causes the B cell to differentiate into plasma cells and into memory cells ***important concept***
- allows plasma cells to to produce free antibody
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What is the role of antibodies
- agglutination
| - precipitation
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What recognizes antigen/antibody complexes
phagocytic cells
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What is an antitoxin
antibody with the ability to neutralize a specific toxin
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What is an opsonin
any molecule that acts as a binding enhancer for the process of phagocytosis
-antibodies can be opsonins
opsonin~helper
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What is the basic structure of an antibody
consist of two high molecular weight polypeptide chains called heavy chains and two lower molecular weight polypeptide chains called light chains
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What type of bond holds the chains together
disulfide bonds
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What is the Fab- fragment
binding portion, binds the antigen
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What is the Fc- fragment
crystalline fragment, determines the antibody class
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Where is the variable region found on the antibody
at the end of the Fab region
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What is the constant region
encompasses the entire Fc region as well as one domain of both heavy and light chains in the Fab region
60
What is IgG
- monomer
- most abundant immunoglobulin
- agglutinates and precipitates antigen, also can act as antitoxin
- When multiple bind to surface of antigen a specific complement protein binds to FC region to begin complement cascade
- crosses placental barrier to provide passive immunity to fetus
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What is IgM
- pentamer
- Largest immunoglobulin, large size prevents from entering tissue
- first class to be produced in response to antigen
- most efficient class at activating complement cascade
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What is IgA
- pentamer
- found in body secretions
- exists as monomer in blood, but secreted as dimer
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What is IgE
- monomer
- barely detectable in normal blood, most bound via Fc region to mast cells ad basophils
- involved in allergy, triggers release of histamines by binding mast cell
- can cause anaphylactic shock
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What is IgD
- Monomer
- found in low levels in serum, role is uncertain
- primarily found on B cells surfaces where it function as a receptor for antigen
- does not bind complement
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What is the complement system
series of proteins that constantly circulate in blood and tissue fluid
-augment, or complement the activities of antibodies
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What are the characteristics of complements
- complement proteins are always circulating and can be quickly activated
- when activated various complement proteins attach to cell surfaces-forms membrane attack complex
- complement binding prepares cell for phagocytosis
- complement binding can release active substances
- complement binding can lyse cell
67
What is the classical complement cascade
antibody binding to antigen is necessary for cascade
- C1 binds to Fc portion of antibody
- C1 converted to enzyme which splits into C2 and C3
- C3 splits to C3a and b
- C3b combines with C4b2b to create C5 convertase
68
What is the alternative complement pathway
- bypasses portion of classical system b/c no antibody/antigen binding is required
- involves 4 proteins, factors B and D, properdin, and C3
- activated by:
- >plant, fungal, bacterial polysaccharides
- >bacterial lipopolysaccharides
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What are the functions of complements
- formation of membrane attack complex (MAC) that causes cell lysis, especially true when bacteria is antigen
- complement proteins mark antigens and attract phagocytic cells
- complement proteins can act as opsonins
- complement proteins can act as anaphylatoxins leading to anaphylaxis
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What can occur if complement is not controlled
vascular damage and initiation of coagulation
| -following initiation of coagulation, components of coagulation are consumed and destroyed, results in hemorrhage
71
What is the primary immune response
- the first response to a particular antigen
- the adaptive immune system requires 1 week or more to respond
- first antibody produced during adaptive immune response is IgM then IgG
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Whatis an T cell independent antigen
do not require presentation, rather B cells respond directly to antigen
73
What is a T cell dependent antigen
require presentation to helper T cell
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What is the secondary immune response
- memory cells are stimulated consequently the adaptive immune response occurs only after a short delay
- level of IgG is higher and longer lasting
- less antigen needed to elicit response of immune system
- memory may persist for years
