Diversity vs. Specificity: Immunoglobulins

Question 0

immunoglobulin structure

Answer 0

two identical heavy and two identical light chains

Question 1

immunoglobulin

Answer 1

aka antibody

can be membrane bound or secreted

all antibodies made by a single cell and have specificity

Question 2

IgM

Answer 2

surface bound antibody

Question 3

Immunoglobulin superfamily

Answer 3

IgM, T cell receptor, MHC (HLA) and Ig-alpha/Ig-beta

Question 4

clonal selection

Answer 4

gene rearrangement events in the absence of antigen
-in bone marrow or thymus

clone has single specificity

10’7 - 10’11 different clones possible

Question 5

primary immunoglobulin rearrangement

Answer 5

multiple germ line genes
-combinatorial diversification

junctional diversity
-addition of nucleotides during process of joining

Question 6

secondary immunoglobulin rearrangement

Answer 6

somatic hypermutation

-point mutations occur in the fully assembled VJ and VDJ regions

Question 7

somatic hypermutation

Answer 7

happens during the immune response

Question 8

IL-3

Answer 8

secreted by T cells

Question 9

IL-7

Answer 9

necessary for commitment to lymphoid lineages

Question 10

location of heavy chain

Answer 10

chromosome 14

Question 11

two different light chains?

Answer 11

kappa and lambda

Question 12

3’ end of gene?

Answer 12

C (constant regions)

Question 13

5’ end of gene

Answer 13

V (variable regions)

Question 14

what contains D regions?

Answer 14

Ig heavy chain and TCR beta chain

Question 15

how many V regions in heavy chain

Answer 15

about 100 V regions

Question 16

different C regions of heavy chain determine what?

Answer 16

determine the isotype of the Ig

Question 17

what genes in the heavy chain?

Answer 17

many C regions (9 classes)
-exon for domain and the hinge region

many V regions, J regions, and D regions

**Exons expressed / introns not expressed

Question 18

what is in the kappa light chain?

Answer 18

only one C region

V regions have a leader exon and a V exon

several J regions between the V and C regions

Question 19

lambda light chain

Answer 19

4 C regions (with interspersed J regions)

around 30 V regions
-each has a leader region and V region

Question 20

allelic exclusion

Answer 20

have these genes on both mom and dad gene

express only mom/dad heavy and light chain

functional B cells never contain more than 1 heavy or light chain
-essential for specificity

expression of both alleles would render the B cell multispecific

can have Mom light and Dad heavy or vice versa

Question 21

Pro-B cell

Answer 21

right after the stem cell

starts to secrete Rag and TdT enzymes which allow it to go from pro-B cell to pre-B cell

Question 22

rearrangements of a heavy chain?

Answer 22

1 - D region joins with J region (forms DJ) - a random
2 - V region joined to DJ ( no C region yet) - forms VDJ
3 - VDJ is transcribed
4 - pre-mRNA has L-D-V-J and C regions and is spliced

• *C-mew and C-delta are the constant regions
  
  • make IgM and IgD, respectively

5 - mRNA is translated in the cytoplasms and the leader is removed as protein transported into the ER
-heavy chain is assembled with light chain

Question 23

mechanism of DNA rearrangement?

Answer 23

flanking the V, J, and D exons are RSS sequences
-each RSS has a nonamer and heptamer separated by 12 or 23 base pairs (1 or 2 turns)

**recombination only occurs between a 1 turn or 2 turn signal

recombination is catalyzed b Rag1 and Rag2 (VDJ recombinase)

Question 24

RSS

Answer 24

recombination signal sequence flank the V D and J exons during DNA rearrangements

Question 25

Rag-1 and Rag-2

Answer 25

apart of the VDJ recombinase enzyme catalyze the recombination of DNA segments

Question 26

junctional diversity

Answer 26

at the junction of hairpin cleavage - have sticky ends TdT catalyzes the random polymerization of nucleotides without the need for a template have P-nucleotides added on sticky end have N-nucleotides added in non-templated manner

Question 27

TdT

Answer 27

catalyzes addition of nucleotides to the sticky ends of broken gene during rearrangement

Question 28

P nucletides

Answer 28

added asymmetrically to the cleaved ends by TdT

Question 29

N nucleotides

Answer 29

added without a template by TdT

Question 30

pre-B receptor

Answer 30

complex of of the IgM without the surrogate light chains -combined with the Ig-alpha and Ig-beta **this is the first checkpoint - if heavy chain rearranged successfully if not successful, cell dies by apoptosis (only 1 in 3 survive)

Question 31

what light chain is made first?

Answer 31

always KAPPA

Question 32

light chain rearrangement

Answer 32

V joins with J ( no D region in light chain) otherwise, mechanism is the same as the heavy chain

Question 33

receptor editing

Answer 33

nonproductive light chain rearrangements can be rescued -check for self recognition by bone marrow if light chain is again not productive (up to 5 for kappa) -depends on which kappa is chosen if all kappa is unsuccessful, will go to lambda light chain **only in the light chains

Question 34

immature B cell

Answer 34

has rearranged heavy and light chain successful if all successful, will release a mature naive B cell

Question 35

alternative splicing

Answer 35

of mew and delta C regions get both IgG and IgM on the surface of B cell

Question 36

components of the B cell receptor?

Answer 36

IgM heavy and light chain, Ig-alpha, and Ig-beta checked by bone marrow stromal cells by presenting self (HLA) - if strong interaction - negative selection - if low affinity - positive selection

Question 37

combinatorial diversification

Answer 37

10'11 possible antibodies not all gene segments are possible pseudogene - accumulated mutations prevent encoding several VDJ segments - no evolutionary pressure -therefore they may be loss during junctional diversity (N and P nucleotides) -may add frameshifts, stop codons, and gobbledy gook

Question 38

junctional diversity

Answer 38

can triple the diversity of genetic sequence alone diversity is generated in the hypervariable region

Question 39

secondary rearrangement diversity

Answer 39

is antigen specific happens in the periphery

Question 40

SCID

Answer 40

mutations in Rag-1 and Rag-2 also by mutation in Il-7