Regulation of the Immune System

Question 1

At the end of an immune response, reduced antigen exposure results in a reduces expression of what? What does this lead to/

Answer 1

IL2 and IL2R

this leads to apoptosis of the antigen-specfici T cells (except for a few that give rise to the memory population)

Question 2

In the absence of “danger” stimuli, immature DCs express low levels of MHC2 and costimulatory molecules. So what happens if a T cell binds to an antigen the APC is carrying in this state?

Answer 2

anergy - which is good because it’s probably carrying a self antigen

Question 3

What percentage of CD4+ cells are usually Tregs?

Answer 3

10%

Question 4

What syndrome results from a genetic lack of Tregs? WHere’s the mutation?

Answer 4

IPEX

mutated transcription factor FOXP3

Question 5

What are the four ways Treg cells can damnpen an immune response?

Answer 5

1. block the effector Tells - makes them unable to produce IL2 or react to it
2. They can soak up IL2 with extra high affinity CD25 so that the other T cells don’t get any and die
3. induce granzyme-mediated apopotis
4. Bind B7 to CTLA4,w hich generates a signal to the dendritic cell to make kynurenin which is toxic to the other T cells in the area

Question 6

How does antigen route of administration affect immune response?

Answer 6

subQ or intradermal: active immune response

IV, orally or aerosol: tolerance or an immune deviation from one type of CD4+ to another

Question 7

What do the Th1 cytokines (IFNgamma, TNFbeta, IL-2) promote?

Answer 7

1. macrophage activation - angry macrophages
2. antibody-dependent cell-mediated cytotoxicity
3. delayed-type hypersensitivity

Question 8

What do the Th2 cytokines (IL2, il5, il9, il10, and il13) promote?

Answer 8

things that help the humoral response:
1. IgG and IgE isotype switching
2. mucosal immunity
3. stimulation of mast cells, eosinophil growth an ddifferentiation
IgA synthesis

Question 9

How can immune complexes SUPPRESS the immune system?

Answer 9

1. Passively administered antibody binds antigen in competition with B cells (so they don’t get a chance to bind antigen with their BCR)
2. IgG can inhibit B cell differentiation by cross-linking the antigen receptor with the Fc receptor on the B cell that has the antigen on its BCR

Question 10

How can immune complexes ENHANCE the immune response?

Answer 10

1. an antigen binds a BCR on a B cell
2. IgM binds to the bound antigen
3. the IgM binding brings in complement, which also binds the antigen
4. The complement interacts with a follicular dendritic cell

this combination of binding augments the immune response

Question 11

How can we regulate the immue response by selective cell mgiration?

Answer 11

different immune cells have different chemokine receptors, so by secreting different chemokines, we can bring specific immune cells to that area

Question 12

What are the chemokine receptors for Th1 cells?

Answer 12

CXCR3 and CCR5

Question 13

What are the chemokine receptors for Th2 cells?

Answer 13

CCR3, CCR4, and CCR8

Question 14

What are the chemokine receptors for Th17 cells?

Answer 14

CCR6

Question 15

Individuals with defects in C1q, C1r and C1s (so the C1 complex) are predisposed to what disease?

Answer 15

systemic lupus erythematosus

Question 16

Deficiency in C3 leads to an increased susceptibility to what type of infections?

Answer 16

bacterial infections and immune complex disease

Question 17

A specific polymorphism in the TLR4 does what for people in Africa? people in Europe?

Answer 17

africa - protective against cerebral forms of malaria

europe - higher levels of pro-inflammatory cytokines that can lead to septic shock - disadvantageous