Defenses and Deficiencies Part 5

Question 1

What is an antigen?

Answer 1

Anything that can bind to the antigen receptor.

Question 2

What can an immature dendritic cell do?

Answer 2

It phagocytoses pathogens

Question 3

What can a mature dendritic cell do?

Answer 3

They can process, package and present the antigen on the cell surface.

Question 4

What makes a dendritic cell move out of the epithelium and into a lymph vessel?

Answer 4

Changes in chemokines and chemokine receptors.

Question 5

What cell does the dendritic cell present to?

Answer 5

Helper T cell

Question 6

What type of antigen does T cell receptors recognize? Can the receptor be secreted?

Answer 6

Small peptides only; No receptor secretion. Do not confuse PRR’s with TCRs

Question 7

What type of antigen does B cell receptors recognize? Can the receptor be secreted?

Answer 7

Proteins, carbohydrates, lipids, and nucleic acids; Can be ‘self’ or foriegn. Secretion of receptor can occur (Antibody not MHC)

Question 8

Describe TCRs.

Answer 8

All TCRs on a single host T cell are identical and bind to a specific antigen peptide with a specific host MHC molecule.

Question 9

TCRs on CD8 T cells bind to which MHC? CD4?

Answer 9

MHC class 1; MHC class 2

Question 10

What kind of MHC molecule is expressed by antigen presenting cell?

Answer 10

Both MHC 1 and 2.

Question 11

How common is the MHC class 1 molecule?

Answer 11

All NUCLEATED cells in the body.

Question 12

How common is the MHC class 2 molecule?

Answer 12

ONlY professional APCs; Dendritic cells, macrophages, and B cells; Also express MHC class 1.

Question 13

Are all the antibodies on a B cell identical?

Answer 13

YES.

Question 14

Describe the adaptive immune response to a extracellular pathogen.

Answer 14

The pathogen is phagocytosed, presented to CD4, which in turn activated macrophages and B cells.

Question 15

Describe the interaction between a macrophage and a CD4.

Answer 15

1. Macrophage eats extracellular antigen
2. Presents with MHC class 2 to CD4.
3. CD4 secretes cytokines
4. Activates macrophage and destroys phagocytosed antigen.

Question 16

Describe the interaction between a B cell and a CD4.

Answer 16

1. BCR binds extracellular antigen
2. ENDOCYTOSED presented in MHC class 2 to CD4
3. CD4 secrets cytokines
4. Activates B cells to make antibodies (IgG)

Question 17

Describe the presentation process for MHC class 2.

Answer 17

1. Extracellular pathogen in eaten by APC
2. Endosome fuses with lysosome (Phagolysosome); Pathogen introduced to hydrolytic enzymes.
3. MHC class 2 molecule is made in the ER (unstable)
4. Invariant chain is stabilizes MHC class 2 molecule in ER.
5. Vesicle with MHC-Invariant chain combines with Phagolysosome
6. Invariant chain is degraded except for small portion (CLIP).
7. HLA-DM removes CLIP so antigen can bind MHC molecule.
8. Peptides are loaded onto MHC class 2 and presented on cell surface to CD4.