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Host and Defense > EXAM 2 T Cells: Development > Flashcards

EXAM 2 T Cells: Development Flashcards

1
Q

T cell progenitors develop in the ___ and migrate to the ___

A

bone marrow, thymus

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2
Q

positive and negative selection occurs in the ___

A

thymus

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3
Q

mature T cells migrate to the ___

A

peripheral lymphoid organs

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4
Q

activated T cells migrate to ___

A

sites of infection

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5
Q

T-cell precursors rearrange their T cell receptor genes in the ___

A

thymus

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6
Q

immature T cells that recognize ___ receive signals for survival. those that interact ___ with self antigen are removed from the repertoir.

A

self MHC, strongly

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7
Q

mature T cells encounter ___ in the peripheral lymphoid organs and are ___

A

foreign antigens, activated

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8
Q

___ are developing T cells within the thymus

A

thymocytes

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9
Q

describe gamma delta T cells

A
  • maintain tissue integrity
  • do not express CD4 or CD8 co-receptors
  • interact with non classical receptors
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10
Q

describe CD4 T cells

A
  • helper T cells
  • several subtypes: Th1, Th2, Th17, Tfh, and Treg
  • regulate adaptive and innate immune function
  • interact with MHC class II
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11
Q

describe CD8 T cells

A
  • cytotoxic T cells
  • direct effector function
  • interact with MHC class I
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12
Q

the ___ is the site of all T cell development

A

thymus

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13
Q

TCR development occurs within the ___ of the thymus

A

cortex

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14
Q

positive and negative selection occurs as thymocytes move from ___ to ___

A

cortex to medulla

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15
Q

what happens to the thymus as you age?

A

it involutes

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16
Q

what are the half lives of CD4 and CD8 T cells?

A
  • CD4 T cells - 4.2 years
  • CD8 T cells - 6.5 years
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17
Q

the thymus involutes with age, resulting in reduced T cell production, but T cell-mediate immunity is not grossly affected. why?

A

the long life span of individual T cells and diversity of TCRs is sufficient to provide immunity even after the loss of T cell production as the thymus involutes with age

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18
Q

T cell progenitors don’t commit until they reach the ___

A

thymus

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19
Q

give an overview of T cell development, including check points

A
20
Q

thymic location influences ___

A

T cell development

21
Q

describe how thymic location influences T cell development

A
22
Q

describe how gene rearrangement dictates T cell lineage

A
  • beta, gamma, and delta genes rearrange first
  • gamma or delta rearrangement suppresses beta and alpha
  • gamma:delta T cells leave the thymus with little selection
  • beta chain production drives CD4 and CD8 expression
    • double positive
23
Q

___ formation initiates the ___ lineage

A
  • beta chain
  • alpha:beta
24
Q

describe how beta chain formation initiates the alpha:beta lineage

A
25
Q

beta chain rearrangement forms the ___

A

pre-TCR

26
Q

describe beta chain rearrangement

A
  • occurs first
  • four attempts
    • two attempts per locus
    • two genes
  • the beta chain locus is organized differently than immunoglobulin chains
  1. Vbeta - Dbeta - Jbeta → Vbeta - DJbeta
  2. Vbeta - DJbeta → VDJbeta
27
Q

describe how beta chain rearrangement forms pre-T cells receptors

A
  • first checkpoint
  • beta chain binds a surrogate alpha chain analogue (pTalpha)
  • assembles CD3 complex
  • signaling drives further development
    • RAG function halts
    • proliferation
28
Q

alpha chain rearrangement occurs in ___

A

pre-T cells

29
Q

the alpha chain locus can sustain many attempts at a ___

A

functional rearrangement

30
Q

describe alpha chain rearrangement

A
  • occurs in pre-T cells
  • follows proliferation and CD4/8 expression
  • may still develop into gamma:delta T cells
  • alpha chain rearrangement excludes gamma:delta T cells
  • rearrangement of an alpha chain gene always eliminates the linked delta chain locus
31
Q

which thymocyte has no CD4 or CD8?

A

double negative thymocytes

32
Q

which thymocytes have both CD4 and CD8?

A

double positive thymocyte

33
Q

___ and ___ matures thymocytes

A

positive and negative selection

34
Q

what do positive selection and negative selection do?

A
  • positive selection - functional TCR
  • negative selection - no self-antigen binding
35
Q

describe positive and negative selection that matures thymocytes

A
36
Q

___ selection ensures MHC is bound

A

positive

37
Q

during positive selection, ___ cells present MHC I/II: self-peptide complexes. ___ must bind MHC within 3-4 days (alpha chain rearrangement can occur, and binding turns off RAG1/2 complex). weak or no binding of TCR to MHC results in ___, whereas moderate or strong binding results in ___. this is the ___ checkpoint.

A
  • epithelial
  • TCR
  • apoptosis
  • survival
  • second
38
Q

___ selection determines CD4 or CD8 expression

A

positive

39
Q

___ selection prevents self-antigen binding

A

negative

40
Q

during negative selection, ___ and ___ present self peptides. moderate binding allows the T cell to ___. excessive binding induces ___.

A
  • dendritic cells and macrophages
  • live
  • apoptosis
41
Q

following selection, T cells are considered ___. at this point, they can still undergo ___

A
  • naive and mature
  • differentiation
42
Q

mature, naive T cells enter the ___

A

blood stream

they enter a draining lympho node by two routes: in the blood or in the afferent lymph coming from an upstream lymph node

43
Q

___ is the signaling component of the TCR

A

CD3

44
Q

cortical epithelial cells in the thymus release ___, which is a signaling molecule that tells T cells that they are in the right spot and induces responsivity to ___. these signals allow a ___ to become a ___.

A
  • notch1 - T cell transcription factor complex
  • IL-7
  • these signals allow an uncommitted T cell progenitor to become a double negative thymocyte committed to the T-cell lineage
45
Q

during beta rearrangement, what happens if delta:gamma rearrangement happens before beta rearrangement?

A

the T cell will become a delta:gamma T cell

the same is true for alpha rearrangement - if delta:gamma rearrangement occurs before alpha rearrangement, it will be come a delta:gamma T cell

delta:gamma T cells are not as common as alpha:beta

46
Q

during beta chain rearrangement, which protein is turned off to allow for proliferation?

A

RAG

it is then turned back on after proliferation

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