Adaptive Antigen Recognition

Question 1

BCRs are composed of

Answer 1

Surface Ig and two invariant chains Iga, Igb- ensure surface expression of Ig and function in signal transduction

Question 2

TCR composed of

Answer 2

a/b heterodimer

Associated proteins form CD3 complex- ensures surface expression of TCR and involved in signal transduction

Question 3

Clonal selection

Answer 3

Gene rearrangement events occur in absence of antigen

Question 4

Somatic hypermutation

Answer 4

Point mutations occurring in fully assembled VDJ regions during an immune response. Provides a significant source of Ab diversity
Does NOT occur in TCRs

Question 5

Light chain gene rearrangement vs heavy chain

Answer 5

Light chain only has V-J segments, heavy chain has V-D-J segments
Heavy- first, D and J are joined, then V is joined to DJ
In TCRs- the beta chain has VDJ, the alpha chain only has VJ

Question 6

RAG-1 RAG-2

Answer 6

Recombination activating genes, facilitate the joining of V, D and J segments

Question 7

Junctional diversity

Answer 7

Insertion of a series of nucleotides, catalyzed by TdT
P nucleotides- added to asymmetrically cleaved hairpins in a templated manner
N nucleotides- added in non templated manner
-Leads to further diversity in the 3rd hypervariable region (idiotype)

Question 8

Stem cell maturation into pro B cell

Answer 8

IL-7 tells stem cell–>pro B cell

Stem cell is only CD43+

Question 9

Pro-B cell

Answer 9

CD43+
CD19+
CD10+
No Ig expression still
Beginning to express RAG and TdT

Question 10

Pre-B cell

Answer 10

Recombined H chain gene, u mRNA
Expresses Pre-B receptor associated u
CD43+
No response to Ag

Question 11

Immature B cell

Answer 11

Expresses low amount of membrane IgM (u + kappa/lambda light chain)
CD43- negative
Response to Ag strong = negative selection, receptor editing
Response to Ag weak = positive selection

Question 12

Mature B cell

Answer 12

Alternative splicing of VDJ-C RNA to form Cu and Cd mRNA
Expresses IgM and IgD
Activated by antigen recognition

Question 13

Allelic exclusion

Answer 13

An individual B cell can express only one heavy chain encoded by one of the two inherited alleles
-Maintains clonal specificity

Question 14

Signals from pre-BCR are responsible for

Answer 14

Largest proliferative expansion of B lineage cells during B cell development
Irreversibly inhibit rearrangement of Ig heavy chain (allelic exclusion)

Question 15

Receptor editing

Answer 15

If there is reaction to self Ag, Light chains will be further rearranged by RAG
Does not occur in T cells

Question 16

Where would you find immature CD3+4+8+ double positive thymocytes, and Mature single positive thymocytes

Answer 16

In the thymic cortex and corticomedullary junction for double positive immature
Thymic medulla/corticomedullary junction for mature

Question 17

Stem cell T cell

Answer 17

Activated by IL-7
CD44+
ckit+
CD25- negative
Located in bone marrow, migrates to thymus

Question 18

Pro-T cell

Answer 18

CD44+
CD25+
ckit+

Question 19

Pre-T cell

Answer 19

Recombined b chain gene
Expresses Pre-T receptor w/b-chain/pre-Ta
ckit+
CD25+
CD44- negative

Question 20

Double positive T cell

Answer 20

Recombined b/a chain genes
Expresses membrane a/b TCR
CD4+, CD8+, TCR/CD3 expression low
Undergo positive/negative selection

Question 21

Signals from Pre-TCR are responsible for

Answer 21

Stimulate a-chain recombination
Irreversibly inhibit rearrangement of b-chain locus on the other chromosome (allelic exclusion)
-Individual can only express one b-chain from one allele

Question 22

Treg cells

Answer 22

Small population of self reactive CD4+ T cells become Tregs
Function to inhibit self-reactive Th1 cells in periphery
Express CD4 and CD25
FoxP3 transcription factor