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125 Cards in this Set

  • Front
  • Back
The portion of the TCR which is invariant; the same from cell to cell
CD3 and zeta chains
The TCR cannot be expressed on the cell surface without
the form of the Ab which recognizes the antigen
membrane-bound Ig
the form of the Ab which eliminates the Ag in the effector phase
secreted Ig
required for structural integrity and effector functions
constant domains which are conserved among clones
has one V and 3-4 C regions depending on the Ab
the heavy chain
the Fc is involved in
effector functions
the FAB is involved in
Ag recognition
the two types of Ab light chains do not differ in their
isotypes differ in their
physical and biological properties and effector functions
Ag-Ab interactions require
noncovalent interactions
allows the two Ag binding FAB regions to move allowing them to bind epitopes further away
hinge region
ability of an Ab site to react with only one Ag epitope
when an Ab binds to a structurally similar Ag
coreceptors of the TCR
CD4 or CD8
T-cell activation requires coreceptors binding to
nonpolymorphic regions on MHC molecules
bind the greatest variety of Ag with highest affinity (low concentrations required for neutralization)
the reason accessory molecules are required for T-cell activation
the affinity of TCR's is low
3 processes involved in lymphocyte maturation, common for both B and T cells
proliferation of immature lymphocytes is stimulated by __, made in the stromal cells
B/T cell with no portion of receptor
pro-B/T cell
B/T cell which expresses one chain of Ag receptor (1/2 of the receptor)
Pre-B/T cell
B/T cell which delivers signals for proliferation
Pre-B/T cell
B/T cell which expresses the complete Ag receptor
Immature B/T cell
Mature B/T cells which do NOT recognize self Ag are said to undergo
failure of position selection
the diversity of the expression of B/T Ag receptors is generated during
somatic recombination of gene segments which code for V regions
only the Ig heavy chain and the TCR-beta loci contain; whereas ALL Ag receptors contain V, C, and J genes
diversity (D) gene segments
limited by the no. of V, D, and J genes in the genome
combinatorial diversity
diversity of Ag receptors is maximized by
unlimited junctional diversity
process of adding or removing nucleotides from V, D, J segments of genes
junctional diversity
hallmark of pre-B cells
expression of cytoplasmic mu heavy chain
each B cell only expresses Ig from one of the two inherited parental alleles
allelic exclusion
assures that B cell expresses receptors of a single specificity
allelic exclusion
immature B cells must express __ to survive
functional IgM (complete heavy and light chains)
designates a mature B cell capable of responding to Ag in the peripheral lymphoid tissue
coexpression of IgM and IgD
if a B cell binds to self Ag with high affinity and DOES NOT undergo apoptosis; this can occur
reactivation of recombinase for a second (different)light chain; receptor editing
progenators of T cells which do not express CD4 or 8
pro-T cells or double-negative T cells
double-negative T cells must express _ to survive
TCR beta chain
after the beta chain of the T cell is expressed; allelic exclusion occurs and subsequently
the alpha chain is formed
the T cell which expresses the beta chain only
the pre-T cell
double-positive immature T cells express
CD4 and 8 and complete alpha and beta chains
weak recognition of class II MCH and peptide by a double-positive immature T cell yields
mature CD4+ (single-positive T cell)
role is to combat infections by INTRACELLULAR microbes
cell-mediated immunity, mediated by T lymphoctyes
two ways microbes can enter cells
viruses bind and replicate in cytoplasm
where naive T lymphocytes first encounter processed protein Ags
peripheral lymphoid organs
once a T cell recognizes an Ag it responds by
producing cytokines which bind on the T cell's own cytokine receptors; this leads to proliferation
IL-2 is a
IL-2 binding to the IL-2 receptor on the T cell leads to (along with 1st and 2nd signals)
rapid clonal expansion
when naive T cells become effector cells
the immune system returns to basal resting state once
Ag is eliminated and effector T cells die
coreceptors recognize
MHC molecules (rather than peptides)
recognize ligands B7-1/B7-2 on APCs
CD28 on the Helper T cell
LFA-1 receptor on the T cell binds __ to strengthen the binding to APC
TCR is clonally distributed while __ are exactly the same from cell to cell (invariant)
accessory molecules
provides the first or initiating signal for T cell activation
CD4/8 binding to MHC molecule
CD4 coreceptor only recognize __ and will only bind
extracellular Ag, MHC class II
ensure that the correct T cells respond to the correct types of microbes
CD4/8 specificities for different MHC molecules
2nd signals required for T cell activation
costimulators (CD28:B7)
on T cells, can increase cytokines (IL-12) and increase B7 expression, leading to increased chance of costimulation (CD28:B7)
CD40 binding to its receptor
why would blocking CD28:B7 or CD40:CD40L be useful in grafting and transplantation?
without this second signal, T cells are not activated
induce expression of costimulators on APCs to secrete cytokines that help activate T cells
adjuvants (ex: CD40)
most adjuvants are products of
microbes or subs that mimic microbes
regarding the TCR complex, the TCR recognizes the Ag while the CD3 and zeta chain
transduce signals
aside from the normal peptide-MHC complex; T cells can also be polyclonally activated by
Abs specific for TCR or CD3
CHO-binding proteins
purpose of adhesion molecules
to increase binding (normally low) of TCR to peptide-MHC complex for a sufficient amount of time to initiate a signal
adhesion molecules are aka
most important factor in the binding of T cells to APC
in resting (naive) T cells, integrins like LFA-1 are in this state
switches integrins from low affinity to high avidity (conformationally different) binding state
release of chemokines by the APC and binding to receptor on the T cell
integrin LFA-1 binds
first cytokine to be produced by CD4 T cells within 1-2 hours of activation
IL-2 binding to the three-chained IL-2R induces
T cell proliferation
aka T cell growth factor
the reason CD4 cells may help activate CD8 cells be releasing cytokines
CD8 cells do not appear to secrete a lot of IL-2
effector function of the CD4 cell
activation of B cells to produce Ab or activation of macrophages
the reason CD8 cells clonally expand at 10,000x rather than CD4's at 1,000X
CD8 cells actually kill infected cells, not just activate others by secretion of cytokines
the most important cell surface protein involved in the effector function of the CD4 cell is
CD40 ligand (CD40L)
CD40L binds to CD40 on __ for activation
B cells and macrophages (or dendritic cells)
CD40L:CD40 on dendritic cells leads to
increased expression of costimulatory molecules and production of T cell activating cytokines
the most important cytokine produced by TH1 cells is
a potent activator of macrophages
INF-gamma stimulates production of antibody isotypes which promote
phagocytosis (Ab binds to Fc receptors on the phagocyte)
increases expression of MHC II and B7, making better APCs to amplify T cell response
produce IL-4 and IL-5
principal action is switching a B cell to IgE
principal action is activation of eosinophils
especially effective against parasites
eosinophil mediated immunity
TH2 cytokines inhibit
TH1 cell mediated immunity
promotes the differentiation of the T cells into TH1 subset
IL-12 from APC in response to a microbe is this type of response
if a microbe does not induce IL-12 this is induced
differentiation toward TH2
effector CTLs kill by
secreting proteins which create pores in cell membranes and induce DNA fragmentation and apoptosis
do not secrete cytokines or kill infected cells, but can be stimulated to upon subsequent recognition of Ag
memory T cells
time when proliferated cells die after eradication of infection
1-2 weeks, only memory cells then remain
ensures T cells do not respond to harmless proteins
requirement of costimulatory molecules expressed on APC in response to a microbe
IL-12 is secreted from __ to stimulate differentiation to __ which secrete __
macrophages, TH1, INF-gamma
IL-12 ultimately leads to
increased (better) Ag presentation to T cells
seen when differentiation toward one CD4 subset inhibits development of the reciprocal population
play no role in eradication of infections by microbes that are living INSIDE host cells
Ag is first recognized and T cell expansion and differentiation occur
induction phase of T cell mediated immunity
T cells encounter Ag again (2nd time) at the site of infection, resulting in activation of effector functions
effector phase
migrating effector T lymphocytes express high levels of
adhesion molecules
naive T lymphocytes home in the lymph node b/c
L-selectin binds to its ligand on HEVs which are found only in the LN
as part of the innate immune response, macrophages secrete __ and __ which cause increased E and P selectin and ligands for integrins
TNF and IL-1
reason activated T cells stay out of the LN
cells do not express L-selectin required for migration to LN
a cell-mediated response test used to determine previous exposure to an Ag
all nucleated cells in the body express MHC class
a death inducing receptor
express Fas ligand on their cell surfaces which bind to CD95 on target cells
cleave and activate caspases inducing DNA fragmentation and apoptosis
many viruses inhibit MHC class I, reducing loading of peptide into the MHC molecule, this results in
reduced surface expression of MHC class I molecules
HIV works by
direct killing of T lymphocytes
neutralizes and eliminates extracellular microbes and toxins
humoral immunity
naive B lymphocytes express these two Abs
IgM and IgD
when B cells differentiate from IgM to other isotypes with the same Ag specificity
heavy chain class switching
repeated exposure to a protein Ag results in the production of Ab with increasing affinity for Ag
affinity maturation
effector T cells are generated in peripheral lymphoid organs by
activation of naive T lymphocytes
the migration of T cells to the site of infection is independant of
produce ROI and NO that kill microbes
activated macrophages (by INF-gamma)
in the primary response to infection, the major Ab made is
IgM, (and then some IgG)
in the secondary humoral response to Ag, affinity is higher and this Ab is made
memory cells do not secrete
examples of T-independant Ag
(do not require Helper T participation)
polysaccharides, lipids, and other nonprotein Ag
cannot bind to MHC and therefore cannot be seen by T cells
nonprotein Ags
T-ind responses differ in that
little or no isotype switching, affinity maturation and memory cell induction occur