Thrush- Genetics of Immunogloblins

Question 1

what gene segments make up the heavy chain? and light chain?

Answer 1

heavy: V,D, J, C
light: V,J,C

Question 2

is it true that genes in Ab coding are rearranged before Ag stimulation?

Answer 2

yes

Question 3

when Ig gene rearrangement occurs, if the first allele is stopped (non-productive) then the other allele will be re-arranged. what is this process describe?

Answer 3

allelic exclusion. (helps with Ig specificity)

Question 4

what does it take for healthy B cells to leave the bone marrow?

Answer 4

healthy heavy chain goes to the surface of the B cell to rearrange the kappa light chain genes. After that the B cell can produce IgM and IgD

Question 5

in C region selection which Ig is co-expressed?

Answer 5

IgD. (it follows IgM)

Question 6

12/23 bp rule describes what?

Answer 6

describes how the heptamer is joined to nonamer

Question 7

what enzyme would lead to the separation of the 12/23 structure if it is mutated?

Answer 7

RAG enzyme

Question 8

what enzyme adds back nucleotides (bases) in the “joining” region; and only really expressed in heavy chain rearrangement?

Answer 8

Terminal deoxynucleotidyl transferase (Tdt)

Question 9

generally an antigen requires both the heavy and light chain to bind too. can an antigen bind to just the L chain or just the H-chain?

Answer 9

yes

Question 10

is Tdt responsible for adding bases via P-addition?

Answer 10

no Tdt adds bases via N-addition (because they are not coded for by the original DNA; P-addition bases are added in as palindromes)

Question 11

what is it called when mutation occurs in a mature B cell? and at what rate does this occur?

Answer 11

somatic hypermutation.

10^-3 bp/generation (hypermutation)

Question 12

affinity maturation allows the B cell to bind its antigen better. so when Igs with highest affinity are selected, what is it referred to as?

Answer 12

immunodominance

Question 13

what does differential RNA processing in the H chain allow?

Answer 13

determines if the protein will me membrane bound or secrete. and allows for simultaneous expression of IgM and IgD

Question 14

if B cell class switches does the VDJ domain also switch?

Answer 14

no

Question 15

can memory cells switch to plasma cells?

Answer 15

yes. if that memory cell (B cell) is exposed to a new Ag it can develop into a plasma cell by cytokines.

Question 16

can IL-4 and IL-5 help to switch to IgE?

Answer 16

yes

Question 17

can a cell switch back once it has already switched downstream?

Answer 17

nope. B cell cell can not produce an upstream isotype to go back

Question 18

if B cell is going to secrete an antibody, than the polypeptide will interact with which chain in order to produced a secreted antibody? what about the other chain

Answer 18

the light chain.

an mRNA that has the secrete signal cut off will produce the heavy chain polypeptide

Question 19

what will a B cell express prior to interacting with its antigen?

Answer 19

co-express IgM and IgD