Maturation and Activation of T cells Flashcards
what is RAG
recombination activating gene
severe combined immune deficiency (SCID) patients have a mutation in what
RAG1 and RAG2
what is TCR
T cell receptor
what do TCRs recognize
peptides displayed by MHC molecules
T/F TCR on each T cell clone is able to bind many peptides
False. TCR on each T cell clone is specific for a distinct peptide
what makes up the immune repertoire?
collection of distinct clones
describe the structure of TCR
membrane-bound heterodimeric protein composed of an alpha chain and a beta chain
there is a variable region and a constant region
where is the binding site for MHC I molecules
variable domain of alpha chains
where is the binding site for MHC II molecules
variable domains of alpha and beta chains
what is recognized by the TCR
1-3 residues of the peptides (processed antigen recognized)
what accounts for the diversity?
somatic recombination of gene segments
within the chains, what does V, D, J, and C stand for
variable
diversity
joining
constant
what does the TCR beta chain contain
variable, short diversity, joining and constant gene segments
what does the TCR alpha chain contain
variable, joining and constant gene segments. No short diversity
where are the D and J gene segments located
between V and C gene segments
during recombination are the segments selected precisely or randomly
random
what is the recombination mediated by
lymphocyte-specific VDJ recombinase (RAG) that brings two segments close together
what are the 3 steps in recombination
- recombination of D and J segments
- recombination of V segments with fused D-J element
- recombination of C segment with fused V-D-J element
note: no D segment in alpha chain
what else leads to the increasing diversity
exonucleases - remove nucleotides
terminal deoxyribonucleotidyl transferase (TdT) - transfers nucleotides
where do T cells mature
thymus
how can a Pro-T cell be described and what does that mean
double negative
means CD4- and CD8-
what promotes cell survival in maturing T cells
pre-TCR and complete TCR
how can an immature T cell be described as what does that mean
double positive
means CD4+ and CD8+
T/F maturing T cells that do not express functional receptors will die
True. Pre-TCR and TCR are both needed for survival
what kind of recognition of MHC+ peptide leads to positive selection
weak recognition
what kind of recognition of MHC+ peptide leads to cell death
no recognition and strong recognition
weak recognition of class II MHC + peptide leads to what kind of cell
mature CD4+ cell
weak recognition of class I MHC + peptide leads to what kind of cell
mature CD8+ cell
T/F the appropriate amount of antigen recognition in the thymus allows T cells to be selected and migrate to the periphery
True
where do naive T cells circulate in search of antigens
from lymph node to lymph node
what occurs after antigen recognition to a naive T cell
proliferation and differentiation
After effector T cells migrate to antigen sites in tissues they get:
reactivated and carry their function
(to keep cells @ site of infection)
T/F antigen recognition (signal 1) alone is sufficient
False. antigen recognition (signal 1) alone induces unresponsiveness
what provides signal 2 to induce proliferation of T cells
engagement of B7 (present on surface of APC) by CD28 (present on surface of T cells)
what is produced by T cells to help clones proliferate
IL-2
what are the three inhibitory signals and their receptors
B7-2 binds to CTLA-4
PD-L1 and PDL-2 bind to PD-1
why are the inhibitory receptors important
critical for limiting/terminating immune response
how does activation of CD4 T cells provide help to CD8 T cells
IL-2 production. IL-2 produced by CD4 helper T cell
T/F antigen-specific T cell clones expand in response to antigen to provide large pool of effector cells to fight infection
True
which t cells increase in number the most
CD8 cells
where do memory cells reside
lymphoid organs and mucosal and peripheral tissues
T/F most effector T cells do not leave LN
False. Most leave the lymph node
which T cells do not leave the LN
follicular helper T cells (Tfh) - they help B cells
what is the function of CD4 helper T cells in cell-mediated immunity
activate phagocytes via IFNy production and CD40-CD40L
where is CD40 present
on macrophage and/or B cell
where is CD40L present
on CD4+ T cell
what is the function of CD4 helper T cells in humoral imunity
activate B cells to produce Ig via cytokine production and CD40-CD40L
what allows for T cell movement
combination of adhesion molecules and chemokine receptor
what is S1P
sphingosine 1-phosphate
how do T cells exit LN
upregulate S1PR1 and follow S1P gradient
(downregulate S1PR1 to stay in LN)
