T-cell mediated immunity: pg 34-36

Question 1

What are the principal cells involved in cellular immunity?

Answer 1

APCs
T cells
Macrophages

Question 2

Cellular immunity involves T cell-mediated killing of target cells and is directed at what 3 types of things?

Answer 2

Tumor cells
Virus infected cells
Chronic infections in general

Question 3

A TCR is always found in association with the protein _____.

Answer 3

CD3

Question 4

What does CD3 do?

Answer 4

Assists in the activation of the T cell following binding of the Ag.

Question 5

What assists in the stabilization of CD3-TCR/Ag-MHC complex?

Answer 5

CD4 and CD8

Question 6

_____ is found on T helper cells.

Answer 6

CD4

Question 7

CD8 is found on ______.

Answer 7

Cytotoxic T cells

Question 8

CD4+ T cells will bind Ag only if it is presented on a class ___ HLA molecule.

Answer 8

Class II

Question 9

CD8+ T cells will bind Ag only if it is presented on a class ___ HLA molecule.

Answer 9

Class I

Question 10

What HLA Class is found on almost all cell types and what (CD4/8) recognizes it?

Answer 10

All cells can express Class I HLA due to the ability of all cells to be inhabited by viruses. CD8+ T cells (CTLs) recognize and bind to these cells.

Question 11

What HLA class is found on cells of the immune system? What CD recognizes it?

Answer 11

Class II HLA molecules can only be expressed on their surface by cells of the immune system (APCs). They are recognized by CD4+ T cells (T helper cells).

Question 12

What is the first signal needed to activate a naive or virgin T cell?

Answer 12

CD3-TCR/Ag-MHC

This signal primes the T cells - if the primed cells do not receive the second signal within a certain time interval, they will become anergic, or unable to be activated.

Question 13

What is the second signal needed to activate a naive or virgin T cell?

Answer 13

B7

This is expressed on the surface of the APC when the cell has encountered bacterial products.

Question 14

Dendritic cells express B7 constitutively, where as __________ and __________ must be stimulated by bacteria.

Answer 14

Macrophages and B cells

Question 15

What is the receptor on the T cell for B7?

Answer 15

CD28

Question 16

What is another co-stimulatory signal that is often released by macrophages following an encounter with LPS?

Answer 16

Interleukin-1 (IL-1)

Question 17

What cells are LPS found on?

Answer 17

Gram negative bacterial cell walls

Question 18

Are dendritic cells phagocytic?

Answer 18

No

Question 19

T/F - Dendritic cells express both HLA class I and II molecules on their surface.

Answer 19

True

Question 20

What other molecules are expressed on the surface of dendritic cells?

Answer 20

ICAM-1, ICAM-2, LFA-1 and LFA-3

They all assist in stabilizing the binding of T cells

Question 21

T/F - Dendritic cells are not easily infected by viruses.

Answer 21

False - They ARE easily infected. Because of this they present viral antigens in the context of HLA class I molecules

Question 22

B cells must be induced to express ___ by bacterial products, in order to activate naive T cells by themselves.

Answer 22

B7

Question 23

After receiving both signals, the naive T cell is activated and secretes ___.

Answer 23

IL-2

Question 24

What does IL-2 do?

Answer 24

Activated T cells secrete IL-2 to increase the expression of its own receptor. It causes T hleper cells to proliferate in a process called clonal expansion.

Question 25

__________________________ results in the production of many T cells, each of which is antigen specific and becomes armed effector cells, either T helper or CTLs.

Answer 25

Clonal expansion

Question 26

Do the armed effector T cells need a second signal or co-stimulation?

Answer 26

No, the next time they encounter their antigen-HLA complex they will act on the antigen/cell.

Question 27

What is released by CTLs when the recognize the Class I HLA-Ag complex?

Answer 27

Perforin

This kills the target cell. The CTL will go on to kill other cells presenting the activating Ag-MHC class I complex

Question 28

During an infection, specific T cells, sensitized to antigens from the infecting organism, release soluble factors such as _______________, that activate macrophages.

Answer 28

Gamma Interferon

Question 29

Macrophages are attracted to sites of inflammation by ________________ factors derived from serum, lymphocytes, neutrophils, and fibroblasts.

Answer 29

Chemotactic