Chapter 7 - T cell development (Exam 3) Flashcards
Two lineages that develop in the thymus
a:b (majority)
g:d (minority)
in the cortex of the thymus there are
immature lymphocytes
in the medulla of the thymus there are
mature lymphocytes
Digeorge’s syndrome
thymus does not develop, still have B cells
susceptible to infections
similar to SCID
thymus is ____________ at birth
fully developed
involution
T cell producing tissue is replaced by fatty tissue as you age
does involution/thymectomy impair T cell immunity?
No
mature T cells in the periphery are
long lived and self renewing
double negative lymphocytes
don’t have CD4 or CD8
Notch 1
drives T cell differentiation
what cytokine is crucial for development? who is it secreted by?
IL-7
stromal epithelial cells
Notch 1 is similar to _________ in B cells
Pax5
gamma delta T cell receptor has _________ diversity than alpha beta T cell receptor
less
unlike ab T cell receptor, gd T cell receptor can bind
peptide without MHC
gene rearrangements in alpha and beta chains
alpha - V-J rearrangements
beta - DJ, VDJ rearrangements
gene rearrangements in gamma and delta chains
gamma: VJ rearrangements
delta: DJ, VDJ rearrangements
Step 1 of competition of gene rearrangements in T cells
g,d chains rearrange vs b chain rearranges
whoever finishes 1st continues
only about _________ of all thymocytes do not undergo apoptosis
2%
first checkpoint of T cell development
assembly of pre-TCR
ensures allelic exclusion has occurred
after the beta chain rearranges and the pre-TCR binds, functional B chain expresses
CD4 and CD8
double positive thymocyte
expresses both CD4 and CD8
pTa
surrogate light chain in the Pre-T-cell receptor
pre T cells
productively rearranged B chains –> temporarily express RAG –> allelic exclusion –>
induced to proliferate –> express CD4 and CD8 –> stop proliferating
step 2 competition of T cell development (if beta chain rearrangement occurs)
gd rearrangement vs alpha rearrangement
committed alpha beta T cell occurs after
both the beta chain and alpha chain rearrangement occur
2nd checkpoint in T cell development
test if alpha chain binds beta chain and assembles TCR
early T cell development in the thymus results in
double positive thymocytes and a functional TCR
Th-Pok
transcription factor
pushes DP cells to CD4 only
positive selection in T cells
select for cells that bind self MHC
negative selection in T cells
select against cells that bind self peptide
positive selection of T cells occurs in ___________ cells only
why?
alpha beta
gamma delta does not recognize peptide/MHC complex
only _________ of DP thymocytes bind to self MHC
2%
when the receptor binds to self peptide/MHC class I, which T cell forms?
when it binds to self peptide/MHC class II?
CD8
CD4
AIRE
autoimmune regulator
helps with negative selection
TF that allows thyme antigen presenting cells to express certain self antigens expressed in non-thymus tissue
what happens when there is a deficiency in AIRE?
T cells attack organs due to recognizing self peptides
central tolerance
inside thymus
peripheral tolerance
outside thymus
two methods of peripheral tolerance
recognition of self antigen will inactivate auto reactive T cell
Treg suppresses auto reactive T cells
Treg (supressor T cell)
suppresses dendritic cell activation of T cells
suppresses T cells by releasing cytokines
self reactive Treg cells are present in
circulation of all people
2 characteristics of Treg
CD25
FoxP3
final phase of T cell differentiation
T cell binds to antigen in secondary lymphoid tissue
T cell leaves thymus, It is ________ but still __________
mature
naive
when T cell binds specific antigen it then
divides and differentiates into effector cell
