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Bio 4650 Midterm 2 > Lymphocyte Development > Flashcards

Lymphocyte Development Flashcards

1
Q

Cells entering the thymus

A

are not yet committed to becoming a lymphocyte and express no antigen-specific receptors

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2
Q

Cell leaving the thymus are

A

mature-functional T cells and express antigen specific T cell receptors

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3
Q

TCRs are both

A
  1. self-tolerance (-)

2. Restricted to self- MHC (+)

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4
Q

Where do T cells develop

A

thymus (primary lymphoid organ)

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5
Q

Early T-cells precursor development occurs in

A

bone marrow

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6
Q

From the bone marrow the T-cell precursors

A

go to the thymus then to the medulla

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7
Q

T-cell double negative

A

cell has no CD4 or CD8 (CD4-CD8-)

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8
Q

T-cell double positive

A

Is both CD4+CD8+

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9
Q

T-cell positive/negative

A

stages for a cell to become single positive CD4+ or CD8+

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10
Q

Functional mature T-cells are released?

A

peripheral bloodstream

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11
Q

Recombination of the TCR gene segments occurs where?

A

Double negative stage

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12
Q

T cell development occurs in two stages

A
  1. Early thymocyte development

2. T cell maturation

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13
Q

NOTCH

A

commits cells to the T cell lineage

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14
Q

CD25

A

receptor for IL-2

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15
Q

Beta-selection

A

results in proliferation and after this occurred the thymocytes are at the DP stage of development

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16
Q

Early thymocyte development

A

where V(D)J recombination happens

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17
Q

T cell maturation

A
  • positive selection

- negative selection

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18
Q

Positive selection

A

select thymocytes bearing receptors capable of binding self-MHC molecules with low affinity resulting in MHC restriction

19
Q

Negative Selection

A

Selects against thymocytes bearing high-affinity receptors for self-MHC/ peptide complexes, resulting in self-tolerance

20
Q

cTEC

A 
cortical thymus epithelial cells express high levels of MHC class 1 and 2 on their surface
-Cortex
21
Q

DP learn MHC restriction in

A

the thymus

22
Q

Three possible outcomes when T cells encounter set-peptide/MHC

A
  • Cant bind (going to be deleted by neglect)
  • Bind too strongly (self react, die by apoptosis)
  • Bind just right (just right to CD4+ or CD8+)
23
Q

Positive selection ensures

A

MHC restriction

24
Q

Negative selection ensures

A

self-tolerance

25
Q

AIRE

A

Autoimmune regulator

  • induces expression of many tissue-specific proteins in medullary thymus epithelial cells
  • binds epigenetic marks on histones to recruit transcription factors
26
Q

Clonal deletion

A

apoptosis in cells with too strong anti-self signaling/ binding

27
Q

Another mechanism for self-tolerance

A
  • Treg, characterized by the expression of FoxP3

- Self-antigen hidden

28
Q

Treg cells

A
  • Deplete the local area ot stimulations cytokines
  • Produce inhibiting cytokines
  • inhibit APC activity
  • Directly kill T cells
29
Q

Peripheral mechanisms

A
  • self antigens are hidden because APCs lack the correct co stimulatory molecules needed to initiate immune responses
  • Some self-antigens are presented by non-APCs, preventing initiation of autoimmunity
  • Strong self-antigens signaling through the TCR in the absence of costimulation may drive T cells into anergy
30
Q

Characteristics of T cells

A
  • Two selections (positive- MHC restriction negative- Self tolerance)
  • Lineage commitment (CD4 vs CD8)
  • Genetic recombina9tion TCR
  • T-cell commitment (NOTCH)
  • Thymus
31
Q

B-cell development occurs

A

starts in the bone marrow and is completed in the periphery

32
Q

B-cell selection

A

only negative

33
Q

B-cell development in the bone marrow

A
  • Stem cells differentiate into many cell types

- Stromal cells provide support and growth factors to developing cells

34
Q

B-cell development

A

occurs in stages that are defined by cell-surface markers, transcription factor expression, and Ig gene rearrangements

35
Q

pre-pro B cells

A

B220+

- No V(D)J recombination

36
Q

Pro-B cells

A

V to DJ recombination

CD19+

37
Q

Pre-B cells

A
  • IgM expression on cell surface

- IL-2R (CD25)

38
Q

Immature B cells

A

leave the bone marrow , naive

39
Q

B-cell tested against self-antigens possible outcome

A
  • Clonal deletion
  • Receptor editing
  • anergy
40
Q

Clonal deletion

A

strongly auto reactive cells by apoptosis

- central tolerance

41
Q

Receptor editing

A

reactivation of light-chain recombination

- central tolerance

42
Q

Anergy

A

induction of non responsiveness

43
Q

Mature B-cells

A
  • migrate to lymphoid follicles
  • Express IgD/IgM
    mRNA spicing determines which one
44
Q

B cell characteristics

A
  • Bone marrow
  • negative selection
  • Require Cell help and secrete antibodies
  • BCR genetic recombination
  • Different subsets

Bio 4650 Midterm 2 (6 decks)

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