2. Immunogenetics Flashcards
components of the BCR
surface Ig and two invariant chains (Igalpha and Igbeta)
components of the TCR
alpha:beta heterodimer (receptor), CD3 chains (epsilon: gamma and zeta:zeta chains) (signaling)
heavy chain recombination for b cells is analogous to what structure in t cells
beta chain of t cells : heavy chain of b cells
somatic hypermutation only occurs in
TCRs
light chain (alpha chain of T cells) undergoes
V to J rearrangement d
heavy chain (beta chain of T cells) undergoes
D to J rearrangement followed by V to DJ rearrangement
recombination signal sequences direct
VDJ recombo through
1) giving recognition enzymes a place to cut and rejoin DNA
2) ensuring gene segments join in correct order
enzyme responsible for recombining V,D, and J segments with the help of RAG-1 and -2
V(D)J recombinase
RAG does what
Recombination activating genes - helps V(D)J recombinase do its thing by binding to hairpin loop to get cut off
enzyme that catalyzes the random polymerization of nucleotides without the need for a template
Terminal deoxyribonucleotidyl transferase adds N nucleotides
TdT (looks like TNT)
as opposed to N nucleotides, P nucleotides are added in
an asymmetric manner to the ends of cleaved hairpins that serve as templates
the process of inserting nucleotides between the D and J segments in the third hypervariable region is known as
junctional diversity
in addition to recombination, receptor chains possess another form of combinatorial diversity in the form of
joining of receptor chains - two receptor chains are needed to make the Ag binding site
CD43+, CD19+, CD10+ cells that also express RAG and TdT
Pro-B cells - forming receptor still
b cell that possesses a surrogate light chain
Pre-B cell B220lo, CD43+
mature naive B cells express IgM and IgD on their cell surface because these two products are a result of
alternative mRNA splicing of the transcript for heavy chain
provide signals for naive B cell maturation
Stromal cells
express VCAM (:VLA-4 on lymphoid progenitor)
Express SCF (:Kit on Pro-B)
Express I-L-7 (late pro-b to pre-B)
although t cells mature in the thymus, they originate in
the bone marrow as t cell precursors
double negative T cells exist in what layer of the thymus
subscapular region
double positive t cells exist in what layer of the thymus
cortex
maturation into single positive t cells occurs in what layer of the thymus
cortico-medullary junction
thymic stromal cells are unique in their ability to
express both HLA classes - helping in the maturation of both CD4 and CD8 T cell populations
stage defined by surrogate alpha/beta chain
Pre-T
in general, ______ Ag recognition is selected for and _______ Ag recognition is selected against
weak
strong
immature b cells that recognize multivalent self Ag are
induced to perform apoptosis
B cell light chains can undergo the unique process of ______ if they are self-reactive in order to potentially rescue the clone
light chain receptor editing
if this fails, the b cell will undergo apoptosis
two checkpoints in b cell development `
Pre-B cell receptor - if there is no receptor ==> apoptosis
After light chain rearrangement - if there is no receptor ==> apoptosis
double positive t cells undergo 2 selection events
1) positive selection ensures only cells with TCRs that bind appropriately to MHC molecules on cortical epithelial cells survive
2) negative selection of cells that recognize self
after this selection, t cells may still react with self Ag, but they are MHC restricted
positive selection
after maturation to single positive T cell, they will
migrate out of the thymus via blood venules
some self-reactive CD4+ t cells will undergo differentiation instead of apoptosis and become _____ to do what
Treg cells
inhibit self reactive Th1 cells in the periphery
gene rearrangement in the lymphocyte generative organs is unique because
it occurs independent of Ag
