T Cell Development Flashcards

1
Q

where does early T cell precursor development occur?

A

bone marrow

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2
Q

what happens when cells arrive at the thymus?

A

their T cell receptors are committed to the T lineage by a receptor called Notch

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3
Q

when the T cell precursors arrive at the thymus, what is the stage called and what does it mean?

A
  • double negative stage
  • they lack CD4 and CD8 as well as their T cell receptor is not fully assembled
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4
Q

what are the four types of peptides that are used for T cell receptor assembly?

A

alpha, beta, gamma and delta

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5
Q

which T cells are CD4 or CD8 positive and found in the lymph nodes or spleen?

A

T-alpha-beta

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6
Q

what do T-alpha-beta cells recognize and do?

A
  • protein antigens
  • bind to antigen derived peptides and MHC
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7
Q

what T cells are CD4 or CD8 negative and predominate on the skin and mucosal surfaces?

A

T-gamma-delta

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8
Q

what do T-gamma-delta cells recognize?

A
  • lipid antigens
  • do not use MHC for antigen recognition
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9
Q

what are the four mechanisms to produce a diverse repertoire of antigen-MHC binding sites for T cells?

A
  1. selection of mini genes
  2. recombination
  3. addition and deletion
  4. association of two different chains to form binding sites
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10
Q

do somatic hypermutations occur during T cell binding site production?

A

no

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11
Q

what happens if B-chain rearrangement is productive?

A

it pairs with a surrogate α-chain (called pre-Tα) to form a pre-TCR complex which sends signals that stop further β-chain rearrangement and promote the rearrangement of the α-chain, ultimately forming a complete TCRαβ receptor.

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12
Q

what happens if B-chain rearrangement is non-productive

A

the cell can instead rearrange the γ and δ chains, forming a TCRγδ receptor

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13
Q

what happens when T-alpha-beta cells become double positive?

A
  • they express both the CD4+ and CD8+ that travel through the cortex and are selected based on their affinity for MHC class I and II molecules
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14
Q

what happens if the TCR recognizes and binds to MHC Class I molecules?

A

the cell is instructed to become CD8+ single-positive (SP) (cytotoxic T cell).

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15
Q

what happens if the TCR recognizes and binds to MHC Class II molecules?

A

the cell becomes CD4+ single-positive (SP) (helper T cell).

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16
Q

what are major histocompatibility complex (MHC) molecules?

A
  • self identity molecules that have broad binding specificity that carry many different peptides including self peptides that bind to TCR and CD4/8 domains
17
Q

where is MHC I and II found?

A

MHC I: almost every cell (nucleated)
MHC II: antigen presenting cells

18
Q

CD8 molecules on T cells bind to what domain of MHC I?

A

alpha-3

19
Q

CD4 molecules on T cells bind to what domain of MHC II?

A

beta-2

20
Q

what happens if T cells cannot bind to MHC peptide?

A

they die

21
Q

what happens during negative selection of T cells?

A

-medullary thymic epithelial cells (mTEC) containing autoimmune regulator protein (AIRE) express and present self antigens all over the body
- T cells that bind too strongly to self-antigens are eliminated to prevent autoimmunity.

22
Q

why do somatic hypermutations not occur in T cells?

A

mutations lead to loss of MHC recognition after MHC selection and the T cells cannot receive signals from antigen-presenting cells

23
Q

how do T-gamma-delta cells arise?

A

If the TCRβ gene rearrangement is unsuccessful the thymocyte will attempt to rearrange the TCRγ and TCRδ genes where the cell assembles a TCRγδ receptor and becomes a Tγδ cell.

24
Q

how do NKT cells arise?

A

During TCRαβ thymocyte development, specific signals (including interaction with CD1d-presenting cells) guide a small subset to commit to the NKT cell lineage instead of the conventional CD4+ or CD8+ T cell lineage

25
Q

what are some characteristics of TCR-gamma-delta lymphocytes?

A
  • appear early in ontogeny, required for protection of the young
  • protect barrier from outside/used in the first line of attack
  • do not recognize (antigen+MHC)
  • recognize protein and non-protein lipid antigens
26
Q

what are NKT cells?

A
  • heterogeneous group of T cells with a TCR assembled with an invariant alpha chain and limited number of beta chains that border between innate and adaptive defense
27
Q

what do NKT cells bind and react to?

A
  • bind foreign and self lipids and glycolipids
  • react to lipid antigens presented by CD1 and release large quantities of cytokines