Antigen receptors and MHC

Question 1

BCR

Answer 1

B-cell receptor:

a surface membrane-bound form of IgM

Question 2

Each Ig light chain has:

Answer 2

3 segments:
~ variable (V)
~ joining (J)
~ constant (C)

Question 3

Each Ig heavy chain has:

Answer 3

4 segments:
~ V
~ J
~ C
~ diversity (D)

Question 4

Each B-cell expresses X chain genes…

Answer 4

one light
one heavy
different combinations of these and combinations of their individual parts create the diversity of BCR

Question 5

RAG1/RAG2

Answer 5

lymphoid-specific enzymes which catalyse V(D)J recombination by recognising RSSs

Question 6

Allelic exclusion

Answer 6

if a productive gene rearrangement occurs in one allele and the expression of the other is silenced

Question 7

Alternative splicing

Answer 7

joining the same variable region to a different constant region

Question 8

MHC

Answer 8

Major histocompatibility complex:
encodes class I and II (function in antigen presentation to T-cells) and III molecules

Question 9

MHC Class I

Answer 9

~ 3 alpha and 1 beta membrane domains

~ 1 Transmembrane segment

Question 10

MHC Class II

Answer 10

~ 2 alpha and 2 beta membrane domains

~ 2 Transmembrane segment

Question 11

Haplotype

Answer 11

tightly linked genes that are generally inherited as a single unit

Question 12

Polymorphic

Answer 12

many alleles exist for each gene in the population

Question 13

Polygenic

Answer 13

Several different MHC genes exist in an individual

Question 14

Co-dominantly expressed

Answer 14

Both maternal and paternal copies are expressed

Question 15

MHC Class II expression is…

Answer 15

restricted to antigen-presenting cells

Question 16

MHC Class I expression is…

Answer 16

seen in each nucleated human cell which can express several unique class I molecules (each with diff binding specificity)

Question 17

Endogenous processing and presentation pathway

Answer 17

endogenous antigens are degraded into peptides w/in the cytosol by proteasomes, assembled with class I molecules in the RER and presented on the membrane to CD8+ T-cells

Question 18

Exogenous processing and presentation pathway

Answer 18

exogenous antigens are internalised and degraded w/in the acidic endolytic compartments and combined with class II molecules for presentation to CD4+ T(H)-cells

Question 19

Cross-presentation

Answer 19

when exogenous antigens in certain cell types (mainly DCs) can gain access to class I presentation pathways