T Cells: Receptors, MHC, and Antigen recognition Flashcards

(33 cards)

1
Q

what are the two major classes of T cells

A

cytotoxic CD8 T cells

helper CD4 T cells

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2
Q

The T cell receptor

A
primarily bind polypeptides
never secreted
incidence detector
no effector function
interacts with MHC complex 
antigens not recognized in isolation(must bind MHC for signal)
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3
Q

what are the two classes of T cell receptors

A

alpha: beta
gamma: delta

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4
Q

alpha:beta T cells

A
classic T cell
adaptive immunity
common in circulation not tissues
develops and matures in thymus
positive and negative selection
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5
Q

gamma:delta T cells

A
not involve in adaptive immunity
monitor tissue health
common in tissues not circulation
develops, but does NOT mature in thymus
limited positive and negative selection 
-one class
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6
Q

alpha chain of T cell receptor

similar to light chain of Abs

A

V, J, C segments

-junctional diversity

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7
Q

beta chain of T cell receptor

similar to heavy chain of Abs

A

V, J, D, C

-junctional diversity

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8
Q

how many hypervariable/complementarity-Determining per chain?

A

3

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9
Q

TCR genes are rearranged by what enzymes?

A

RAG 1/2 complexes

deficient in RAG leads to no T cells

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10
Q

what has more total diversity between immunoglobulins and alpha:beta receptors?

A

alpha:beta T-cell receptors

why? T cell receptor genome is longer

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11
Q

What do TCRs require for signal transduction?

A

CD3

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12
Q

CD3 complex

A

mediates TCR signaling

-NO TCR expression without CD3 complex

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13
Q

What does the MHC do?

A

presents broken down antigens(peptides) to TCRs

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14
Q

MHC class I

A
found on nearly all cells
**presents intracelluar antigen**
alpha and beta2 microglobulin
**-ER antigen loading**
**CD8 co-receptor
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15
Q

MHC class II

A

internalized (phagocytosis)

  • on antigen presenting cells ( macs, dendritics, and B cells)
  • *vesicular ER loading**
  • *CD4 Co-receptor
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16
Q

what is another name for MHC

A

human leukocyte antigen (HLA)

17
Q

will TCRs bind both MHC class I and II?

A

yes, it is the co-receptor on the T cell that determines MHC class binding

18
Q

what cell does not have any MHC complexes on its surface?

A

erythrocytes and neurons

19
Q

where does loading occur for MHC class I?

20
Q

where does loading occur for MHC class II

A

VESICULAR ER loading

21
Q

cells that express MHC class II can express MHC class I T/F?

22
Q

MHC I: antigen loading in the ER

A
  • heavy chain is stabilized by calnexin until beta 2 binds.
  • heavy chain forms peptide loading complex with calreticulin, tapsin, TAP and ERp57
  • TAP delivers intracellular peptide to Class I heavy chain forming mature MHC I molecule
  • MHC class I dissociates from peptide loading complex and is exported from ER
23
Q

The intracelluar antigen peptides are how many residues?

A

8-10

  • trimmed before expression
  • allows detection of intracellular infection
24
Q

MHC I: cross presentation of endocytosed antigen

A

phagocytic cells that have endocytosed antigen will express both MHC I and II with the same antigen

25
why is cross presentastion important?
important for naive CD8 T cell activation | -also doesn't allow for intracelluar pathogens to live inside phagocytic cells
26
MHC II: CLIP prevents self antigen presentation how?
- invariant chain blocks binding of peptides to MHC II in the ER - once inside a vesicle the invariant chain is cleaved, leaving CLIP fragment bound - CLIP blocks binding of MHC II in vesicle - HLA-DM facilitates release of CLIP, allowing peptides to bind
27
what blocks bind of MHC II in the ER?
invariant chain
28
what blocks the binding of MHC II in the vesicle?
CLIP
29
what releases the binding of CLIP inside the vesicle?
HLA-DM
30
the T cell synapse | what dictates MCH specificity of T cells
the Co-receptors on the T cells | NOT the TCR
31
what MHC does a CD8 bind?
MHC I on any cell with intracelluar pathogen
32
what MHC does a CD4 bind?
MHC II on a APC
33
T cells have a direct and indirect effector function how?
(direct) CD8s bind intracelluar pathogen infected cell to die (indirect) -CD4s bind to APCs to release cytokines (indirect) -CD4s bind to B cells to differentiate into plasma cells to make antibodies