2.5 Flashcards
T cells express ___ that recognize peptides displayed by MHC molecules
T cell receptor (TCR)
TCR on each T cell clone is specific for a ___
distinct peptide
which is the difference between the receptors of the innate and adaptive immunity?
a - both are clonal
b - the receptors of the innate immunity are clonal
c - the receptors of the adaptive immunity are clonal
d - the receptors of the adaptive immunity are not antigen specific
e - the receptors of the innate immunity are antigen specific
c - the receptors of the adaptive immunity are clonal
membrane-bound heterodimeric proteins are composed of alpha and beta chains with ___ and __ regions
- variable
- constant
the TCR binding site has variable domains of alpha chains for ___
MHC class I
the TCR binding site has variable domains of alpha and beta chains for ___
MHC class II
the TCR recognizes ___
processed antigen
how is the diversity of TCR generated?
recombination of V, D, J gene segments
____ of gene segments accounts for diversity of TCR gene loci
somatic recombination
recombination of TCR gene segments occurs through ___
random selection
recombination of TCR gene segments is mediated by _____ that brings two segments close together
lymphocyte-specific VDJ recombinase (RAG)
what is the 1st step of recombination of TCR gene segments
recombination of D & J segments
what is the 2nd step of recombination of TCR gene segments
recombination of V segments with fused D-J element
what is the 3rd step of recombination of TCR gene segments
recombination of C segments with fused V-D-J element
_____ diversity is limited
combinatiorial
____ diversity is unlimited
junctional
what are the ways that junctional diversity is generated
- exonucleases
- terminal deoxyribonucleotidyl transferase (TdT)
- tremendous diversity
Pre-T cells express one chain of antigen receptor called ___
pre-TCR
what are the functions of pre-TCR
- promotes cell SURVIVAL
- triggers TCR alpha gene recombination
immature T cells express ___ that promotes cell survival
complete TCR
immature T cells also express ___ (besides TCR)
CD4 & CD8
in maturation of thymocytes, there are cycles of ___ where cells that do not express functional receptors die
expression of antigen receptors
selected T cells are ___
single positive
weak recognition of ___ leads to selection of T cells
MHC + peptide
what do both strong or no recognition of MHC + peptide lead to
death
how does the appropriate amount of antigen recognition in the thymus impact T cells
allows T cells to be selected and migrate to the periphery
how are T cells specific for an antigen selected in the thymus?
a - upon strong recognition of antigen in thymus, T cells get positively selected
b - upon strong recognition of antigen in thymus, T cells get negatively selected
c - upon weak recognition of antigen in thymus, T cells get negatively selected
d - upon week recognition of antigen in thymus, T cells undergo apoptosis
e - upon lack of recognition of antigen in thymus, T cells get positively selected
b - upon strong recognition of antigen in thymus, T cells get negatively selected
___ circulate from LN to LN in search of their antigens
naive T cells
what occurs after effector T cells have migrated to the antigen sites in tissues
- reactivation
- carry out their function
antigen recognition involves ___ & ___
- proliferation
- differentiation
antigen recognition (signal 1) ALONE induces ___
unresponsiveness
engagement of ___ on APC by ___ on T cells provides signal 2 and induces ___
- B7
- CD28
- proliferation
IL-2 produced by T cells helps ____
clone proliferation
what is critical for limiting / terminating immune responses
inhibitory receptors
___ are induced in activated T cells
inhibitory receptors
concomitant activation of CD4 T cells provides help to CD8 T cells via ____
IL-2 production
antigen-specific T cell clones expand in response to ___ in order to provide ____
- antigens
- a large pool of effector cells to fight infection
where do memory cells reside
- lymphoid organs
- mucosal & peripheral tissues
____ proliferate and differentiate
naive T cells
most ___ leave LN except for ___ which function to help B cells
- effector T cells
- Tfh
what are the effector functions of CD4 helper T cells?
- activate phagocytes via IFN gamma production and CD40-CD40L
- activate B cells to produce Ig via cytokine production and CD40-CD40L
what allows T cell movement
combo of adhesion molecules & chemokine receptors
circulation of T cells is different depending on their activation state. What statement below describes circulation of T cells accurately:
a - naive T cells circulate to the tissues when there is an infection
b - naive T cells circulate to the bone marrow where they encounter their antigens
c - naive T cells circulate to LN to encounter their antigens
d - effector T cells circulate to LN to encounter their antigens
e - memory T cells remain in the LN where they are activated
c - naive T cells circulate to LN to encounter their antigens
what signals are provided by Thelper cells to help macrophages and B cells?
a - CD40L & IL-2
b - CD28 & IL-2
c - CD40 & IL-2
d - DTLA4 & IL-2
e - CD40L & IFN gamma
e - CD40L & IFN gamma
what is the difference between naive and effector T cells in a situation in which there is an infection?
a - only naive T cells circulate in the body
b - effector T cells live for years while naive T cells have a short life
c - naive T cells contract when they do not encounter antigen
d - effector T cells contract following clearance of pathogens
e - effector T cells and naive T cells have a short life
d - effector T cells contract following clearance of pathogens
what the following terms:
1 - CD28
2 - CD 40L
3 - MHC - I
4 - MHC - II
5 - IL - 2
a - CD40 - APC
b - TCR CD4
c - TCR - CD8
d - B7 - APC
e - IL-2R-T cells
1 - d
2 - a
3 - c
4 - b
5 - e
what is necessary for thymocytes to survive and mature in the thymus?
a - expression of CD4 & CD8
b - expression of IL-7R
c - expression of TCR
d - expression of pre-TCR
e - expression of pre-TCR & TCR
e - expression of pre-TCR & TCR
