Module 5 Flashcards

(50 cards)

1
Q

What are the six stages of B cell development?

A
Repertoire assembly
Negative selection 
Positive selection
Searching for infection
Finding infection 
Attacking infection
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2
Q

What is the role of bone marrow strolls cells during early B cell development?

A

They regulate B cell development through the production of IL-7

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3
Q

What are the functions of the surrogate light chain?

A

Blocks further H-chain rearrangement
Signals proliferation
Signals light chain rearrangement

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4
Q

What is allelic exclusion?

A

A cell can only express one of its two gene copies

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5
Q

During B cell development what are the Ig gene recombination steps?

A

Pro B cell - H chain gene rearrangement
Pre B cell - L chain gene rearrangement
Immature B cell - rearrangement ceases

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6
Q

When is a developing B cell considered an immature B cell?

A

When it produces IgM surface receptors and releases from stromal cells into circulation

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7
Q

What Ig’s do immature B cells express?

A

IgD and IgM

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8
Q

What are anergic cells?

A

Nonfunctional B cells that reacted with soluble antigens in the bone marrow, but are released into circulation only to die after a few days.

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9
Q

What is the process of receptor editing?

A

The additional opportunities provided to self-reactive B cells to reorganize their light chains

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10
Q

What happens to developing B cells that despite reorganizing their lights chains are still self reactive?

A

Apoptosis

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11
Q

What is clonal deletion?

A

The death of self reactive developing B cells

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12
Q

What is the process of negative selection?

A

The elimination of self-reactive immature cells

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13
Q

What kinds of lymphocytes undergo negative selection?

A

B and T cells

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14
Q

What is central tolerance?

A

The immunological tolerance to self by B and T cells

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15
Q

What does peripheral tolerance do?

A

The peripheral tissues sometimes catch escaped self reactive B and T cells

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16
Q

What happens to naive B cells after the exit the bone marrow?

A

They head to the lymph nodes for positive selection by the FDC

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17
Q

What does FDC stand for?

A

Follicular dendritic cells, the structural stromal cells that interact with immature B cells and positively select for survival

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18
Q

Final two phases of B cell development depends on what?

A

An encounter with an antigen

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19
Q

What are the four steps that B cells go through in their final development phases in the lymph node?

A
  1. Mature naive B cell encounters Ag
  2. Activation via partnership with Th
  3. Migration to primary follicle
  4. Proliferation and differentiation in German centers
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20
Q

What are the four stages of B cell development that occurs in the bone marrow?

A
  1. Stem cell
  2. Pro B cell
  3. Pre B cell
  4. Immature B cell
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21
Q

What are the five stages of B cell development that occur in the secondary lymphoid organs and circulation?

A
  1. Immature B cell
  2. Mature naive B cell
  3. Antigen-activated B lymphoblast
  4. Antibody secreting plasma cell
  5. Memory cell
22
Q

When the immature B cells leave the bone marrow, which Igs do they have?

A

They start with IgM and IgD

23
Q

Once B cells are in circulation, how do they achieve higher IgM and low IgD?

A

Through alternative splicing to give delta and mi chains then they gain access to primary lymphoid follicle

24
Q

What do nature B cells with low IgM and high IgD do next?

A

Enter circulation and bind antigen in lymphoid tissue draining infection

25
What three steps happen once B cells reach the antigen-activated B lymphoblast stage?
1. Alternative splicing to secret Ig 2. Isotype switching 3. Somatic hypermutation
26
What is the purpose of B cells that have matured to the antibody secreting plasma cell level?
Fights active infections
27
What is the purpose of B cells that make it to the memory cell level?
Prep for a future infection
28
What is a thymocyte?
The T cell precursors that reach the thymus
29
Where is the thymus located?
Above the heart
30
What is the organization of the thymus?
It is sectioned into two regions, the cortex which is on top and densely packed and the medulla which is below and less densely packed.
31
Why do we become more dependent on our pool of mature B cells as we age?
The thymus shrinks with age
32
Are there more alpha-beta T cells or gamma delta T cells?
90-95% alpha beta TCR
33
Why are there four chances for TCR beta chain formation?
Because VDJ happens on the beta chain locus and each allele has two constant regions
34
What does pre-TCR signaling do to developing T cells?
Blocks further beta rearrangement and induced proliferation and expression of CD4 and CD8
35
What does pT alpha chain do for developing T cells?
Acts as a placeholder for TCR alpha chain much like the B cell surrogate chain
36
What are the two checkpoints on T cell development?
1. Rearrangement first on the beta chain otherwise apoptosis 2. Rearrangement second of the alpha chain otherwise apoptosis
37
What percentage of thymocytes do not pass the selection process?
98%
38
What does T cell education refer to?
The processes of positive and negative selection that thymocytes undergo
39
What does positive selection accomplish?
Ensures that only T cells with functional TCRs are capable of interacting with self MHC survive and determine their functional role
40
T cells during positive selection express what on their surface?
CD4, CD8 and TCR
41
How if the effector function determined during positive selection?
If T cell interacts with MHC class 1 then it keeps CD8 and if it interacts with MHC class 2 it is CD4
42
What does the process of negative selection accomplish?
It results in clonal deletion of self reactive T cells
43
How are self reactive T cells identified?
They bind to tightly to thymocytes APCs presenting self and results in apoptosis
44
What does AIRE stand for?
Autoimmune regulatory
45
What is AIRE?
A transcription factor expressed by thymic epithelial cells
46
What is the function of AIRE?
Induced expression of hundreds of tissue specific proteins to present on MHC to developing T cells during education
47
What are the three types of T cells?
CTL, Th and reg
48
What is the difference between tT reg cells and T reg cells?
tT are reg cells matured in the thymus and T reg cells mature in the periphery was
49
What do T reg cells do?
Suppress the action of autoreactive T cells and contributes to peripheral tolerance
50
What are the four stages of T cell development?
1. Proliferation and differentiation of double-positive thymocytes 2. Positive selection (T cell education) 3. Negative selection (T cell education) 4. Entry to circulation