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Host And Defense - Exam 2 > Exam 2 - T Cells - Receptors, MHC, and Antigen Recognition > Flashcards

Exam 2 - T Cells - Receptors, MHC, and Antigen Recognition Flashcards

1
Q

What is the main function of CD8 T cells?

A

Kill virus-infected cells

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2
Q

What is the function of CD4 T1 cells?

A

Activate infected macrophages

Provide help to B cells for antibody production

EXTRACELLULAR BACTERIA

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3
Q

What is the function of CD4 T2 cells?

A

Provide help for B cells for antibody production, esp switching to IgE

Helminth parasites

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4
Q

What is the function of CD4 T17 cells?

A

Enhance PMN response

PROMOTE BARRIER INTEGRITY - MUCOSAL SURFACES

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5
Q

What is the fx of all types of T cells?

A

B cell help

Isotype switching

Antibody production

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6
Q

What is the fx of CD4 regulatory T cells?

A

Suppress T cell responses

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7
Q

What do TCRs (T Cell Receptor) bind?

A

Polypeptides

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8
Q

Where are TCRs expressed?

A

On cell surfaces, never secreted

Similar in structure to immunoglobulins

Interacts with MHC presented antigen

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9
Q

What are the 2 classes of TCRs?

A

Alpha:Beta T Cells

Gamma:Delta T Cells

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10
Q

Tell me about Alpha:Beta T Cells.

A
  • Develop and mature in the thymus
  • “Classic” T cell
  • Adaptive immunity
  • Common in CIRCULATION, not tissues
  • Positive and negative selection
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11
Q

Tell me about Gamma:Delta T Cells.

A
  • Not involved in adaptive immunity
  • Monitor tissue health
  • Common in TISSUES, not circulation
  • DEVELOPS, but does not mature in the thymus
  • Limited positive and negative selection
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12
Q

T/F - T cells only express one type of TCR class, NEVER both.

A

TRUE

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13
Q

CD4 T1 take care of what?

CD4 T2 take care of what?

CD4 T17 take care of what?

A

T1 - Small, extracellular

T2 - Big, multicellular

T17 - Mucosal

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14
Q

T/F - TCR genes undergo rearrangement.

A

TRUE

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15
Q

The alpha chain has what segments on it?

A

V, J, and C segments with junctional diversity

V = Variable
J = Junctional
C = Constant
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16
Q

The beta chain has what segments?

A

V, J, D, and C segments with junctional diversity

D = Diversity

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17
Q

TCRs req the ______ complex for signal transduction.

A

CD3

It mediates TCR signaling, and expression does NOT occur w/o CD3

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18
Q

What fragment is the TCR associated with in signal transduction?

A

Zeta fragment

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19
Q

What does MHC stand for?

A

Major histocompatibility complex

20
Q

What are the two classes of MHC?

A

I

II

21
Q

What antigen does MHC class I target and what cells have MHC I?

A

Intracellular antigen

Nearly all cells have it

22
Q

What parts make up the MHC class I?

A

Alpha chain (alpha 1,2, and 3)

Beta 2 microglobulin

23
Q

What type of antigen loading happens with MHC class I?

A

ER antigen loading

24
Q

CD__ communicates with MHC Class __, while CD__ communicates with MHC Class __.

A

CD8 - MHC Class I

CD4 - MHC Class II

25
Q

MHC Class II targets when antigen type and what cells have MHC II?

A

Internalized antigen

Antigen presenting cells

  • B cells
  • Macrophages
  • Dendritic cells
26
Q

What chains are in MHC Class II?

A

Alpha and beta chains

27
Q

Which type of antigen loading does MHC II do?

A

Vesicular ER loading

28
Q

CD8 receptor binds which domain on MHC Class I?

A

Alpha3

29
Q

The CD4 receptor binds what domain on the MHC II molecule?

A

Beta chain

30
Q

What does the beta 2 microglobulin do for the MHC Class I molecule?

A

Stabilizes the molecule

31
Q

In general, both MHCs do what?

A

Bind peptides for TCR presentation

They are promiscuous, not particular at all

Nearly all cells express some form of MHC
-RBCs are devoid of MHC

32
Q

The following are hematopoietic cells. Which are MHC I and which are MHC II?

T cells
B cells
Macrophages
Dendritic cells
Neutrophils
Erythrocytes
A

T cells - I

B cells - I and II

Macrophages - I and II

Dendritic cells - I and II

Neutrophils - I

RBCs - NONE

33
Q

The following are non-hematopoietic cells and they all express what type of MHC Class?

Hepatocytes

Kidney epithelium

Brain

A

MHC Class I

34
Q

Tell me the process of MHC Class I antigen presentation.

A

Intracellular antigen

Proteasome - Antigen broken down to peptides here

Peptides transported to ER

Peptide bound by MHC Class I

MHC Class I present peptide at cell surface

35
Q

Tell me the MHC Class II antigen presentation.

A

Extracellular antigen

Endocytosis vesicle

Peptides produced in phagolysosome

MHC Class II comes vesicled from ER and meets with phagolysosome

Peptides are bound to MHC Class II w/in phagolysosome

MHC Class II presents peptide at cell surface

36
Q

Tell me the detailed version of MHC I antigen loading in the ER.

A

MHC Class I heavy chain is stabilized by CALNEXIN until beta2-microglobulin binds

CALNEXIN is released and a complex of calreticulin, tapasin, ERp57, and TAP forms.

A peptide is delivered by TAP to the heavy chain - this forms the “mature” MHC Class I molecule

MHC Class I dissociates from the complex and is exported from the ER to the cellular surface

37
Q

MHC I - Antigen Loading in the ER allows for what?

A

Peptides trimmed before expression

Allows detection of intracellular infection

Intracellular peptides are 8-10 residues

38
Q

T/F - Crosspresentation of endocytosed antigen is just that internalized antigen is expressed on MHC Class I and MHC Class II.

A

TRUE

This is important in naive CD8 T cell activation

39
Q

Tell me the detailed version of MHC II - Antigen Loading into vesicles.

A

Antigen is taken from the extracellular space into intracellular vesicles

Early endosomes have neutral pH, and endosomal proteases are inactive

Acidification of vesicles activates proteases to degrade antigen into peptide fragments

Vesicles containing peptides fuse with vesicles containing MHC Class II molecules

40
Q

What prevents self antigen presentation?

A

CLIP

41
Q

Tell me the detailed version of what CLIP does.

A

INVARIANT CHAIN blocks binding of peptides to MHC Class II in ER

Invariant chain is cleaved off in vesicles, but the CLIP portion of the invariant chain remains bound

CLIP blocks binding of peptides to MHC Class II

HLA-DM facilitates release of CLIP, and peptides bind

42
Q

What is CLIP?

A

Class II-associated invariant chain peptide

43
Q

What dictates MHC specificity?

A

Co-receptors

*This is within the T Cell Synapse

44
Q

What happens when a CD8 T cell contacts a virus infected cell?

A

It leads to apoptosis

45
Q

What happens when a CD4 T cell contacts a macrophage?

A

Cytokines released and those activate a macrophage to release their own cytokines

46
Q

What happens when CD4 T cells contact B cells?

A

Cytokines are released and B cells differentiate into plasma cells, and then antibodies are released from the plasma cell

Host And Defense - Exam 2 (16 decks)

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