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SFM Exam 1 > 8: Adaptive Ag Recognition > Flashcards

8: Adaptive Ag Recognition Flashcards

1
Q

How many chains make up BCR vs TCR?

A

BCR: 4 chains
TCR: 2 chains

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2
Q

Signals transducers in BCR and TCR complexes

A

BCR: Iga, IgB
TCR: CD3

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3
Q

First two Igs produced

A

IgM, then IgD

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4
Q

What chain are the constant regions on for Igs?

A

Ig heavy chains

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5
Q

Ig light chains: which is preferred?

A

K (more than a)

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6
Q

What Ag type can T cells bind?

A

Linear, processed peptides bound to HLAs

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7
Q

Analogous regions on TCRs and BCRs

A

BCR heavy chain = TCR B chain

BCR light chain = TCR a chain

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8
Q

Five steps of lymphocyte maturation

A
  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
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9
Q

Three major mechanisms to generate lymphocyte diversity

A
  1. combinatorial diversification (VDJ rearrangement)
  2. Junctional diversity
  3. Somatic hypermutation
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10
Q

Two main steps in combinatorial diversification

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

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

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11
Q

Three mediators of combinatorial diversification

A

RSS, RAG1, RAG2

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12
Q

RSS

A

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

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13
Q

RAG1, RAG2

A

Recombinases that cut sections and join VDJ segments

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14
Q

Where are RAG1 and RAG2 made?

A

Only in lymphocytes

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15
Q

Junctional diversity

A

Additional of nts during the VDJ joining process

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16
Q

What enzyme facilitates junctional diversity?

A

TdT

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17
Q

TdT: two types of nt inserts

A

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

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

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18
Q

Somatic mutation

A

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

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19
Q

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

A

Combinatorial diversification only uses VJ, no D region

20
Q

Second type of combinatorial diversification

A

When combining heavy + light chain randomly

21
Q

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

A

Stem cell factor (SCF) + Kit

22
Q

IL-7

A

The lymphoid survival cytokine

23
Q

Five phases in B cell formation

A
  1. Stem cell
  2. Pro-B
  3. Pre-B
  4. Immature B
  5. Mature naive B cell
24
Q

Six phases in T cell formation

A
  1. Stem cell
  2. Pro-T
  3. Pre-T
  4. Double positive T
  5. Single positive T / immature T
  6. Mature naive T cell
25
Q

Universal B cell marker

A

CD19

26
Q

BCR of a pre-B cell

A

Heavy Mu chain + surrogate light chain

27
Q

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

A
  1. Proliferative expansion of B or T cells

2. Allelic exclusion

28
Q

Allelic exclusion

A

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

29
Q

What does allelic exclusion help maintain?

A

Clonal specificity

30
Q

Negative selection in B and T cells

A

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

31
Q

Tolerance in distinguishing self from non-self

A

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

32
Q

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

A

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

33
Q

What helps B cells develop central tolerance?

A

Receptor editing of self-reactive B cells

34
Q

Does receptor editing occur for T cells?

A

No

35
Q

How does a BCR become either IgM or IgD?

A

Alternative splicing

36
Q

Five co-receptors present on mature B cells

A
  1. CD19
  2. CD81
  3. CD21 (CR2)
  4. CD40
  5. CD20
37
Q

B1 cells

A

Found in mucosa with limited Ag specificity

38
Q

B2 cells: two categories and where theyre found

A

Follicular B cells: recirculating

Marginal B cells: in spleen

39
Q

What type of B cell are the majority?

A

Follicular B cells

40
Q

Thymic stroma

A

Environment for T cell development

41
Q

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

A

Outer region: thymic cortex

Inner region: thymic medulla

42
Q

Cytokine secreted by thymic epithelial cells

A

IL-7

43
Q

Positive Selection for T cells in thymus

A
  1. TCR interacts with class I or II molecule
  2. If no recognition -> apoptosis
  3. If recognition -> become restricted to that cell type
44
Q

Three receptors expressed on Treg cells

A
  1. CD4
  2. CD35
  3. CTLA-4
45
Q

Treg cells

A

Small population of self-reactive CD4 cells

46
Q

Function of Tregs

A

Inhibit self-reactive Th cells in the periphery

47
Q

Two cytokines secreted by Tregs

A

TGF-B, IL-10

SFM Exam 1 (17 decks)

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