8: Adaptive Ag Recognition

Question 1

How many chains make up BCR vs TCR?

Answer 1

BCR: 4 chains
TCR: 2 chains

Question 2

Signals transducers in BCR and TCR complexes

Answer 2

BCR: Iga, IgB
TCR: CD3

Question 3

First two Igs produced

Answer 3

IgM, then IgD

Question 4

What chain are the constant regions on for Igs?

Answer 4

Ig heavy chains

Question 5

Ig light chains: which is preferred?

Answer 5

K (more than a)

Question 6

What Ag type can T cells bind?

Answer 6

Linear, processed peptides bound to HLAs

Question 7

Analogous regions on TCRs and BCRs

Answer 7

BCR heavy chain = TCR B chain

BCR light chain = TCR a chain

Question 8

Five steps of lymphocyte maturation

Answer 8

1. Commitment of progenitor cells
2. Proliferation of progenitors
3. Sequential and ordered rearrangement of Ag receptor genes
4. Selection events
5. Differentiation into effectors

Question 9

Three major mechanisms to generate lymphocyte diversity

Answer 9

1. combinatorial diversification (VDJ rearrangement)
2. Junctional diversity
3. Somatic hypermutation

Question 10

Two main steps in combinatorial diversification

Answer 10

1. Choose J + choose a D -> join these two sections

2. Choose a V -> join to DJ -> VDJ

Question 11

Three mediators of combinatorial diversification

Answer 11

RSS, RAG1, RAG2

Question 12

RSS

Answer 12

Recombination signal sequence; directs recombination, providing recognition sites for RAG1/2 and ensuring gene segments are joined in the correct order

Question 13

RAG1, RAG2

Answer 13

Recombinases that cut sections and join VDJ segments

Question 14

Where are RAG1 and RAG2 made?

Answer 14

Only in lymphocytes

Question 15

Junctional diversity

Answer 15

Additional of nts during the VDJ joining process

Question 16

What enzyme facilitates junctional diversity?

Answer 16

TdT

Question 17

TdT: two types of nt inserts

Answer 17

N (non-template) nts: added randomly between coding joints

P (palindromic) nts: added non-randomly to asymmetrically cleaved hairpins in a templated manner

Question 18

Somatic mutation

Answer 18

Point mutations in BCRs during an immune response, providing lots of Ab diversity - only in B cells though

Question 19

What is different in formation of the light chain/alpha chain compared to heavy chain/B chain formation?

Answer 19

Combinatorial diversification only uses VJ, no D region

Question 20

Second type of combinatorial diversification

Answer 20

When combining heavy + light chain randomly

Question 21

Interaction between what two factors stimulates proliferation of early pro-B cells?

Answer 21

Stem cell factor (SCF) + Kit

Question 22

IL-7

Answer 22

The lymphoid survival cytokine

Question 23

Five phases in B cell formation

Answer 23

1. Stem cell
2. Pro-B
3. Pre-B
4. Immature B
5. Mature naive B cell

Question 24

Six phases in T cell formation

Answer 24

1. Stem cell
2. Pro-T
3. Pre-T
4. Double positive T
5. Single positive T / immature T
6. Mature naive T cell

Question 25

Universal B cell marker

Answer 25

CD19

Question 26

BCR of a pre-B cell

Answer 26

Heavy Mu chain + surrogate light chain

Question 27

Two things signals from pre-B cells and pre-T cells do

Answer 27

1. Proliferative expansion of B or T cells | 2. Allelic exclusion

Question 28

Allelic exclusion

Answer 28

Signals to irreversibly inhibit BCR heavy chain/TCR B chain rearrangement on the other chromosome

Question 29

What does allelic exclusion help maintain?

Answer 29

Clonal specificity

Question 30

Negative selection in B and T cells

Answer 30

B cells are deleted or functionally inactivated if they react with self-Ags T cells are deleted or become Tregs if they react with self-Ags

Question 31

Tolerance in distinguishing self from non-self

Answer 31

immature B cells acquire tolerance when they are challenged with a self-Ag and do NOT become activated

Question 32

If an immature B cell responds to self Ag, how can it be rescued?

Answer 32

By receptor editing: RAG is reactivated and rearranges light chain to try again

Question 33

What helps B cells develop central tolerance?

Answer 33

Receptor editing of self-reactive B cells

Question 34

Does receptor editing occur for T cells?

Answer 34

No

Question 35

How does a BCR become either IgM or IgD?

Answer 35

Alternative splicing

Question 36

Five co-receptors present on mature B cells

Answer 36

1. CD19 2. CD81 3. CD21 (CR2) 4. CD40 5. CD20

Question 37

B1 cells

Answer 37

Found in mucosa with limited Ag specificity

Question 38

B2 cells: two categories and where theyre found

Answer 38

Follicular B cells: recirculating | Marginal B cells: in spleen

Question 39

What type of B cell are the majority?

Answer 39

Follicular B cells

Question 40

Thymic stroma

Answer 40

Environment for T cell development

Question 41

What are the outer and inner cortical regions of the thymus called?

Answer 41

Outer region: thymic cortex | Inner region: thymic medulla

Question 42

Cytokine secreted by thymic epithelial cells

Answer 42

IL-7

Question 43

Positive Selection for T cells in thymus

Answer 43

1. TCR interacts with class I or II molecule 2. If no recognition -> apoptosis 3. If recognition -> become restricted to that cell type

Question 44

Three receptors expressed on Treg cells

Answer 44

1. CD4 2. CD35 3. CTLA-4

Question 45

Treg cells

Answer 45

Small population of self-reactive CD4 cells

Question 46

Function of Tregs

Answer 46

Inhibit self-reactive Th cells in the periphery

Question 47

Two cytokines secreted by Tregs

Answer 47

TGF-B, IL-10