2. Immunogenetics

Question 1

components of the BCR

Answer 1

surface Ig and two invariant chains (Igalpha and Igbeta)

Question 2

components of the TCR

Answer 2

alpha:beta heterodimer (receptor), CD3 chains (epsilon: gamma and zeta:zeta chains) (signaling)

Question 3

heavy chain recombination for b cells is analogous to what structure in t cells

Answer 3

beta chain of t cells : heavy chain of b cells

Question 4

somatic hypermutation only occurs in

Answer 4

TCRs

Question 5

light chain (alpha chain of T cells) undergoes

Answer 5

V to J rearrangement d

Question 6

heavy chain (beta chain of T cells) undergoes

Answer 6

D to J rearrangement followed by V to DJ rearrangement

Question 7

recombination signal sequences direct

Answer 7

VDJ recombo through

1) giving recognition enzymes a place to cut and rejoin DNA
2) ensuring gene segments join in correct order

Question 8

enzyme responsible for recombining V,D, and J segments with the help of RAG-1 and -2

Answer 8

V(D)J recombinase

Question 9

RAG does what

Answer 9

Recombination activating genes - helps V(D)J recombinase do its thing by binding to hairpin loop to get cut off

Question 10

enzyme that catalyzes the random polymerization of nucleotides without the need for a template

Answer 10

Terminal deoxyribonucleotidyl transferase adds N nucleotides
TdT (looks like TNT)

Question 11

as opposed to N nucleotides, P nucleotides are added in

Answer 11

an asymmetric manner to the ends of cleaved hairpins that serve as templates

Question 12

the process of inserting nucleotides between the D and J segments in the third hypervariable region is known as

Answer 12

junctional diversity

Question 13

in addition to recombination, receptor chains possess another form of combinatorial diversity in the form of

Answer 13

joining of receptor chains - two receptor chains are needed to make the Ag binding site

Question 14

CD43+, CD19+, CD10+ cells that also express RAG and TdT

Answer 14

Pro-B cells - forming receptor still

Question 15

b cell that possesses a surrogate light chain

Answer 15

Pre-B cell B220lo, CD43+

Question 16

mature naive B cells express IgM and IgD on their cell surface because these two products are a result of

Answer 16

alternative mRNA splicing of the transcript for heavy chain

Question 17

provide signals for naive B cell maturation

Answer 17

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)

Question 18

although t cells mature in the thymus, they originate in

Answer 18

the bone marrow as t cell precursors

Question 19

double negative T cells exist in what layer of the thymus

Answer 19

subscapular region

Question 20

double positive t cells exist in what layer of the thymus

Answer 20

cortex

Question 21

maturation into single positive t cells occurs in what layer of the thymus

Answer 21

cortico-medullary junction

Question 22

thymic stromal cells are unique in their ability to

Answer 22

express both HLA classes - helping in the maturation of both CD4 and CD8 T cell populations

Question 23

stage defined by surrogate alpha/beta chain

Answer 23

Pre-T

Question 24

in general, ______ Ag recognition is selected for and _______ Ag recognition is selected against

Answer 24

weak

strong

Question 25

immature b cells that recognize multivalent self Ag are

Answer 25

induced to perform apoptosis

Question 26

B cell light chains can undergo the unique process of ______ if they are self-reactive in order to potentially rescue the clone

Answer 26

light chain receptor editing | if this fails, the b cell will undergo apoptosis

Question 27

two checkpoints in b cell development `

Answer 27

Pre-B cell receptor - if there is no receptor ==> apoptosis | After light chain rearrangement - if there is no receptor ==> apoptosis

Question 28

double positive t cells undergo 2 selection events

Answer 28

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

Question 29

after this selection, t cells may still react with self Ag, but they are MHC restricted

Answer 29

positive selection

Question 30

after maturation to single positive T cell, they will

Answer 30

migrate out of the thymus via blood venules

Question 31

some self-reactive CD4+ t cells will undergo differentiation instead of apoptosis and become _____ to do what

Answer 31

Treg cells | inhibit self reactive Th1 cells in the periphery

Question 32

gene rearrangement in the lymphocyte generative organs is unique because

Answer 32

it occurs independent of Ag