lecture 4 - lymphocyte development Flashcards
where do b cells rearrange their genes
in the bone marrow
if the common lymphoid progenitor expressed Pax5 transcription factor it will become what
a b cell
what is CD45 is a marker on what cells
B and T cells
CD19 is a marker of what cell
B cells
what is negative selection
removal of self reactive cells
what causes a mature B cell to be activated
when it binds to a foreign antigen
activated B cells causes the number of which cells to rise
plasma cells and memory cells
where does negative selection of B cells occur
in the bone marrow
what does VpreB and λ5 do
bind to heavy chain and make sure its ok and capable of binding a light chain
what is the first stage of B cell formation
pro-B cell
after V to DJ rearrangement occurs what does the pro-B cell turn into
pre-B cell
after light chain rearrangement the pre-B cell turns into an
immature B cell
signal that the pre-B cell is ok turns off what genes
RAG 1 and 2 so no more heavy chain rearrangement
after the RAG genes are turned off what does the cell do
proliferated a few times
then RAG genes come back on for rearrangement of what
light chain
D-J rearrangement on both chromosomes then
V - DJ rearrangement on first chromosome
if the heavy chain rearrangement is no good you can use the heavy chain rearrangement on
the second chromosome
if it fails on both chomosomes the cell
dies
if it has passed on the to L chain rearrangement stage, you can attempt to make a light chain on kappa locus if that fails you can try on
lamda locus
immature B cells that bind to a self antigen in the bone marrow undergo either
clonal deletion: apoptosis
or
receptor editing: further light chain gene arrangements of variable regions
what are anergic B cells
B cells that bind to soluble self antigens (not on cell surface)
and the B cell down regulates its level of BCR so can escape the bone marrow
cells become unresponsive
common lymphoid progenitor goes into thymus and gets a signal to start doing what
rearranging their t cell receptor genes
T cells expressing TCR must bind with what to be positively selected
self MHC
what protein signals to initiate T cell receptor rearrangements
notch
if TCR recognises MHC it is
positively selected
if TCR recognises MHC too well it is
negatively selected
what are examples of the T cell markers
CD3 CD4 CD8
what are the types of cells in the thymus
lymphoid cells
epithelial cells
macrophages and dendritic cells
which part of the thymus are the t cells positively selected
the cortex
they then move into the
medulla
before t cells come out the thymus that have both ___ and ___ on the surface
CD4 and CD8
what is expressed on all T cells
CD3
where does the CD3 transmits signal to after TCR recognition
the nucleus
γδ T cells dont express what
CD4 or CD8
where are the majority of the γδ T cells located
skin or gut
when the cell goes into the thymus it doesnt have
CD3 CD4 or CD8 (double negative)
if the γδ genes are rearranged it leaves the thymus very quickly and it has which marker
CD3
if αβ genes are rearranged the cells express CD4 and CD8 making them
double positive
the under goes positive selection: cells die if they
dont bind to self MHC
cells survive positive selection if they
do binds to self MHC
they then undergo negative selection:
cells survive id the bind to self MHC
moderately
cells die in negative selection if the bind to self MHC
tightly
if they survive they turn off
either CD4 or CD8 and leave the thymus and go into the blood
where does positive selection take place
cortex
where does negative selection take place
medulla
