Mb #15 - T Cell Activation I

Front 1

What are the two types of TCR?

Back 1

Alpha-beta and gamma-delta.

Front 2

Describe the variable and constant regions of T cell receptors.

Back 2

Variable regions - encoded by V, D, and J genes. Constant regions - C genes only.

Front 3

What happens to TCR genes as T cells mature in the thymus?

Back 3

V, D, and J genes rearrange to form the beta chain V region. V and J genes rearrange to form the alpha chain V region.

Front 4

How are TCRs different from Igs?

Back 4

TCR beta genes sometimes omit the D gene; they do not undergo class switching; and TCRs are much more restricted in their specificities.

Front 5

What are the only protein antigens that TCRs can recognize?

Back 5

TCRs only recognize protein antigens bound to MHC molecules.

Front 6

Which T cells are eliminated during maturation in the thymus?

Back 6

Alpha-beta T cells that do no recognize self-MHC or that recognize self-peptides.

Front 7

Antigen processing = ?

Back 7

Cleavage of antigens to the proper size that they may fit into the MHC molecule groove.

Front 8

__ expression of MHC II molecules is not constitutive? How is expression activated?

Back 8

Macrophages do not express constitutively but expression is up-regulated by interferon-gamma (T cell cytokine).

Front 9

This stimulatory molecule can induce macrophage expression and produce cytokines that may modulate T cell activation. Which cytokines may be released?

Back 9

B7. IL-12, IL-15, and IL-18.

Front 10

__ cells have constitutive MHC II expression. How does this expression influence efficiency for this cell type?

Back 10

B cells. Efficiency is increased.

Front 11

What are the most effective APCs? How do they express MHC II molecules?

Back 11

Dendritic cells. Constitutively expression of MHC II molecules.

Front 12

Langerhans cells are __ cells in the epidermis?

Back 12

Dendritic cells.

Front 13

MHC I molecules process __ antigens but MHC IIs process __ antigens.

Back 13

MHC I - intracellular antigens. MHC II - extracellular antigens.

Front 14

What constitutes antigen processing?

Back 14

Degradation of antigens by cellular proteases.

Front 15

Where are MHC II molecules synthesized and assembled? What binds to the MHC II in this location?

Back 15

ER. Invariant chain binds to the MHC II here.

Front 16

What is the effect of invariant chain binding to MHC II during its assembly?

Back 16

IC blocks endogenous peptide binding to MHC II molecule and guides the MHC II to the exocytic pathway.

Front 17

Which antigens are commonly found in the cytosol?

Back 17

Viral or tumor antigens.

Front 18

Why can almost any cell infected by tumor or virus produce antigens for CD8 cells?

Back 18

Most cells express MHC I molecules, which process intracellular agents, which are often tumor and viral cells.

Front 19

What is the purpose of TAP?

Back 19

Transports antigen fragments into the ER, where MHC I molecules are synthesized.

Front 20

What does calnexin do? When does it become independent?

Back 20

Calnexin stabilizes MHC I molecules as they are synthesized in the ER.

Front 21

What happens when peptide antigens bind to MHC I molecules?

Back 21

Calnexin separates from the MHC I, leaving the antigen-MHC I complex to exocytose.

Front 22

Which has more specific binding: MHC-antigen complexes or antibody-TCR complexes?

Back 22

Antibody-TCR complexes have more specificity.

Front 23

What determines the ability of a peptide to bind and bind securely to an MHC molecule?

Back 23

The size and amino acid sequence of the peptide.

Front 24

What limits the antibody response to an antigen?

Back 24

Activation of T-helper cells (activated by an associated peptide antigen).

Front 25

__ transmits the intracellular signals for TCR and is always expressed with it. Where does the association between these two take place? What pathway do they take?

Back 25

CD3. Association takes place in the ER. They take the exocytic pathway.

Front 26

Which T cells produce cytokines and which ones mediate cytotoxicity? Which antigen-MHC complex do they recognize?

Back 26

CD4 (helper cells) produce cytokines; recognize MHC II. CD8 (cytoxic cells) mediate cytotoxicity; recognize MHC I.

Front 27

LFA-1 is a __ molecule. To what does it bind? What increases its avidity?

Back 27

Adhesion molecule. It binds to ICAM-1. Interaction between TCR and APC increase LFA-1’s avidity.

Front 28

Name the T cell accessory molecule and the ligand that help increase the possibility of co-stimulation.

Back 28

CD 28 (accessory molecule) and B7 (ligand).

Front 29

What does the binding of CD40L to CD40 stimulate?

Back 29

Expression of CD80 and CD86 (co-stimulatory molecules).

Front 30

How is induced mrna stabilized during intracellular signaling?

Back 30

CD80 or CD86 bind on the APC to CD28 on T cell.