1 PCOL 838B IMMUNE SYSTEM I AND II EXAMS QUESTIONS AND ANSWERS
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1 PCOL 838B IMMUNE SYSTEM I AND II
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1 PCOL 838B IMMUNE SYSTEM I AND II
1 PCOL 838B IMMUNE SYSTEM I AND II
what is innate immunity - Answer- -rapid response (hours)
-fixed
-limited number of specificities
-constant during respone
what is adaptive immunity - Answer- -slow response (days to weeks)
-variable
-numerous highly selective specificities
-...
1 PCOL 838B IMMUNE SYSTEM I AND II
what is innate immunity - Answer- -rapid response (hours)
-fixed
-limited number of specificities
-constant during respone
what is adaptive immunity - Answer- -slow response (days to weeks)
-variable
-numerous highly selective specificities
-improve during response
examples of innate immunity - Answer- -anatomical barriers: physical and chemical barriers
-phagocytic cells: patrol bloodstream and tissue and rush to site of infection
-complement: direct activities of some phagocytic cells
what are the main adaptive immune organs - Answer- spleen
lymph nodes
thymus
bone marrow
lymph nodes - Answer- -similar to spleen
-germinal center contains rapid proliferation of B cells
-lymphoid follicle (mostly B cells)
spleen - Answer- like giant lymph node
-filters blood to sense blood borne pathogens
what are the physiologic events during inflammatory events - Answer- -healthy skin is not inflamed
-surface wound introduces bacteria, which activate resident effector cells to secrete cytokines
-vasodilation and increased vascular permeability allow fluid, protein and inflammatory cells to leave blood and enter tissue
-the infected tissue becomes inflamed, causing redness, heat, swelling and pain
T cells - Answer- -thymus derived immune lymphocytes
-main constituent of the lymphocyte population
-diversity and specificity determined by: TCR and CD profile and cytokine profile
how is antigen captured and presented to immune system to sense an antigen via lymph node and spleen in adaptive
immunity - Answer- -lymph node captures antigen from epithelium and connective tissue
-blood-borne antigens are captured by antigen presenting cells in the spleen
T cell vs B cell in binding to an antigen - Answer- -unlike the B-cell receptor (aka membrane bound immunoglobulin) the T
cell receptor (TCR) can not bind to a free floating antigen that it happens to brush against
-the T cell receptor can only bind to a protein antigen that has been processed into a very small peptide, and then packaged
inside of a special cell protein called MHC or major histocompatibility complex
-the edges of TCR recognizes the edges of MHC and the center of the TCR recognizes the specific invader peptide (small
protein fragment)
how do MHCs work - Answer- -the T cell receptor from a "individual A" will only recognize antigens presented by MHC
from individual A (MHC genes are very polymorphic, the MHC from individual B will have different amino acid sequences
and will not be recognized by the TCR of individual A)
-like the B cell receptor (eg membrane bound IgM) each TCR is pre-designed" through gene rearrangement to have affinity
for aq particular antigen, but there are lots and lots of T cells each sporting a different TCR
what are the two types of MHCs - Answer- MHC class I
MHC class II
what are the two types of T cells - Answer- CD4 (helper) cells
CD8 (killer) cells
MHC class II - Answer- -MHC class II is composed of two protein chains, an alpha chain with two domains and a beta
chain with two domains
, -CD4 only recognizes antigen presented by MHC class II b/c the CD4 TCR complex contains protein co-receptors that
recognize the beta 2 domain found in MHC class II
MHC class I - Answer- -MHC class I is composed of two protein chains, an alpha chain with three domains and a second
protein chain, beta-2 microglobulin
-CD8 TCR only recognizes antigen presented by MHC class I b/c the CD8 TCR complex contains protein co-receptors that
recognize the alpha 3 domain found in MHC class I
what cells express which MHCs - Answer- -virtually all cells express MHC class I
-only a handful professional cells express MHC class II
-only activated T cells express MHC class II, resting T cells don't
-in brain, microglial cells express MHC class II
class II MHC pathway vs class I MHC pathway for composition of stable peptide MHC complex - Answer- class II:
polymorphic alpha and beta chains, peptides
class I: polymorphic alpha chain, beta2-microglobulin, peptide
class II MHC pathway vs class I MHC pathway for types of APCs - Answer- class II: dendritic cells, mononuclear
phagocytes, B lymphocytes; some endothelial cells, thymic epithelium
class I: all nucleated cells
class II MHC pathway vs class I MHC pathway for responsive T cells - Answer- class II: CD4 + T cells (helper T cells)
class I: CD8 + T cells (CTLs)
class II MHC pathway vs class I MHC pathway for source of protein antigens - Answer- class II: endosomal/lysosomal
proteins (mostly internalized from extracellular environment)
class I: cytosolic proteins (mostly synthesized in the cell; may enter cytosol from phagosomes)
what are the T cell effector functions of class II MHC - Answer- -macrophage activation: destruction of phagocytosed
microbe (long-term)
-B cell antibody secretion: antibody binding to microbe
what are the T cell effector functions of class I MHC - Answer- -killing of antigen expressing infected cell
how many versions of MHC genes are there
what does the diversity of MHC genes mean - Answer- -there are literally hundreds of versions (or alleles) of the MHC
genes in the human population. of those, you would have only inherited somewhere around 10 or so from your parents
-this diversity means that it is highly unlikely that you have the same MHC versions as the person next to you
-b/c different MHC versions have different peptide binding characteristics for assembling and displaying foreign peptides,
this diversity may be an evolutionary selection so that within the population some of the population will be able to survive a
given microbial exposure (if your MHC cannot bind the bugs peptide and present it, you cannot have a good immune
reaction to it)
humoral immunity vs cell mediated immunity - Answer- -humoral immunity: block infections and eliminate extracellular
microbes
-cell-mediated immunity: activate macrophages to kill phagocytosed microbes; kill infected cells and eliminate reservoirs of
infection
physical features of an antibody protein - Answer- -a single antibody protein molecule is composed of two identical light
chains and two identical heavy chains (the light is not identical to the heavy), joined by disulfide bonds
-each light and heavy chain has a constant region at the C-termius (every protein has two ends to its amino acid chain, a C-
terminus and an N-terminus), which does not vary much in amino acid sequence between different B cells antibodies
-each light and heavy chain has a variable regions at the N-terminus. this variable region varies greatly in amino acid
sequence between the antibodies of different B-cells (this variable region is the at the heart of the billions of different
antibody-attached B cells prepared in advance by the immune system)
linear epitope vs discontinuous epitope - Answer-
what is the antibody structural features that vary - Answer- varying amino acid sequences and number of domains
contribute to isotypic variation
variable region of B-cell/antibody binding - Answer- -variable region defines the billions of different B-cell/antibody binding
specificities prepared in advance
-important to understand that for a single B-cell (for example a B-cell that has been stimulated by antigen to begin
proliferating and mounting an antibody response, has T cell help, etc) its own particular antibody binding specificity (variable
region) can be attached onto different constant regions of the heavy chain. early in the process it is always the "M" ehavy
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