T-cell immunity

Question 1

What is the main role of T cell immunity?

Answer 1

Destroy intracellular pathogens

Question 2

What types of intracellular pathogens are targetted by T cell immunity?

Answer 2

Bacteria that escape death by phagocytosis

All viruses

Question 3

What types of antigens do TCRs bind to?

Answer 3

ONLY protein antigens, specifically peptide fragments

Question 4

Does it matter that TCR can only bind to peptide fragments?

Answer 4

No, because all microbes express protein antigens

Question 5

TCRs bind to what on self cells?

Answer 5

MHC molecules - major histocompatibility complexes

Question 6

TCR binding to MHC-peptide complex is based on what?

Answer 6

Structural fit

Question 7

The primary immune response generates what kinds of T cells?

Answer 7

Effector T cells (From naive T cells), which, after the infection is done, some of these will remain as memory cells

Question 8

What happens to the vast majority of T cells after an infection has been dealt with?

Answer 8

They undergo apoptosis

Question 9

Peptides that are presented on MHC molecules are derived from what?

Answer 9

Derived from proteins on intracellular pathogens

Question 10

What type of MHC molecule does a CTL bind to?

Answer 10

MHC1

Question 11

What type of MHC molecule does a Th cell bind to?

Answer 11

MHC2

Question 12

What type of MHC molecule does a CD8+ cell bind to? CD4+?

Answer 12

MHC1 - cytotoxic

MHC2 - helper

Question 13

MHC class 1 molecules present peptides generated….?

Answer 13

in the cytoplasm of infected cells

Question 14

What type of pathogens would be presented on MHC1 molecules?

Answer 14

All intracellular viruses, and some intracellular bacteria

Question 15

What type of cells have MHC class 1 molecules?

Answer 15

All nucleated cells

Question 16

What are the different ways to escape phagocytosis?

Answer 16

Block fusion of phagosome with lysosome, be resistant to acids/enzymes, leave phagosome and enter the cytoplasm.

Question 17

How are peptides from intracellular pathogens presented on MHC 1 molecules?

Answer 17

Pathogen enters cell, cytoplasmic proteins of the pathogen are degraded by the proteasome into peptides. These peptides are then attached to MHC1 molecules and gets presented to a CTL.

Question 18

_______ __ ______ bind to peptides presented on MHC class 1 molecules.

Answer 18

Cytotoxic T cells

Question 19

____ _____ ___ molecules present peptides generated in a cell vesicle.

Answer 19

MHC class 2

Question 20

What type of cells present MHC class 2:peptide complexes?

Answer 20

Antigen presenting cells (APCs)

Question 21

What are the different APCs of the body?

Answer 21

Macrophages, mature dendritic cells, B cells

Question 22

How do APCs present peptides on MHC2 molecules?

Answer 22

Ingest extracellular pathogen by phagocytosis. These are degraded by lysosomal contents into peptides. Peptides are bound to MHC2 molecules and presented to T helper cells.

Question 23

Why are neutrophils not APCs?

Answer 23

Lifespan is too short

Question 24

How does a B cell, then, internalize pathogens?

Answer 24

B cell internalizes extracellular pathogen by endocytosis.

Question 25

Describe, broadly, endocytosis into presentation on MHC2.

Answer 25

Protein antigen binds to receptor, endocytosis occurs, placed in endosome. Endosome fuses with lysosome, protein degraded into peptides. presented on MHC 2.

Question 26

_______ __ ______ bind to peptides presented on MHC class 2 molecules.

Answer 26

Helpter T cells

Question 27

What is peculiar of APCs in terms of which cells they can interact with?

Answer 27

Have both MHC 1 and MHC 2 molecules and can thus interact with both Th cells and CTLs.

Question 28

Under what conditions would APCs use MHC1 molecules? MHC2?

Answer 28

MHC1 - if infected

MHC2 - phagocytosis/endocytosis

Question 29

What type of cell, is the ONLY cell that can activate naive T cells to generate effector T cells?

Answer 29

Dendritic cells

Question 30

Which cells can be considered the innate cells that initiate adaptive immunity?

Answer 30

Dendritic cells - only cells that can activate naive T cells