Mucosal Immunity (Exam 3)

Question 1

3 special challenges of the GI regional immune system.

Answer 1

1. tolerance of food antigen
2. tolerance of commensal bacteria while respond to pathogens
3. large surface area

Question 2

What is the first layer of defense in regional immune systems? How does it prevent microbial invasion?

Answer 2

outer epithelial barrier
tight junctions

Question 3

Give two examples of specialized lymphoid tissue distinct to the mucosal immune system.

Answer 3

1. peyer’s patches
2. tonsils

Question 4

Regional immune systems have specialized cell types not abundant in other areas of the immune system. Provide this cell type for skin and for the GI tract.

Answer 4

skin: Langerhan’s cells
GI: M cells

Question 5

What is the major function of M cells?

Answer 5

sample antigen from GI lumen for T cell activation

Question 6

What two processes do M cells use to sample antigen from the GI lumen?

Answer 6

endocytosis & phagocytosis

Question 7

What two locations are adaptive immune responses initiated in regional immune systems?

Answer 7

unencapsulated MALT
distant lymph nodes

Question 8

Homing T cells in GALT back to the gut is mediated by:

Answer 8

vitamin A

Question 9

When a GALT naive T cell in the gut is activated, it is exposed to ________ by dendritic cells. This allows it to express what two things for homing purposes?

Answer 9

retinoic acid (RA)
CCR9 + integrin a4B7 (alpha4beta7)

Question 10

Activated T cells in GALT of the gut express CCR9, a chemokine receptor, and integrin a4B7 so it can return home after entering the circulation. What two molecules are expressed on endothelial cells that allow T cells to bind when it needs to come home?

Answer 10

CCL28 (ligand for CCR9)
MadCAM (adhesion molecule + ligand for a4B7)

Question 11

List the 2 functions of Th17 cells in GI mucosal immunity.

Answer 11

1. maintain epithelial barrier integrity
2. protect from extracellular bacteria

Question 12

Th17 cells function to maintain integrity of the GI epithelial barrier by producing what two cytokines?

Answer 12

IL-17
IL-22

Question 13

What do Th17 cells produce that protects the GI tract from extracellular bacteria?

Answer 13

antibmicrobial peptides

Question 14

If Th17 cells are overactive in the intestinal tract, what does this lead to?

Answer 14

irritable bowel disease (IBD)

Question 15

In certain parts of the body, inflammation can be lethal so they have evolved to be more tolerant to foreign antigen. What is this concept called?

Answer 15

immune privilege

Question 16

What parts of the body have immune privilege? (5)

Answer 16

brain, eye, testes, placenta, fetus

Question 17

(T/F) One part of immune privilege is that the immune system has limited access to antigen in these regions of the body.

Answer 17

True

Question 18

In areas with immune privilege, a mechanism to dampen inflammation is immunosuppressive _________.

Answer 18

cytokines

Question 19

(T/F) Lymphocytes in immune privileged regions are rerouted to better serve other areas of the body but do not undergo cell death.

Answer 19

False - inactivated and/or killed

Question 20

What two molecules are in the eye can be used to kill or suppress lymphocytes to limit inflammation?

Answer 20

Fas ligand
PD-1

Question 21

(T/F) The blood-brain barrier is an example of immune privilege.

Answer 21

True

Question 22

Which antibody functions in gut immunity?

Answer 22

IgA

Question 23

What is the main function of IgA in gut immunity?

Answer 23

prevent both commensal and pathogenic microbes from invading bast epithelial lumen

Question 24

________ migrate to the lamina propria of the gut and secrete IgA.

Answer 24

plasma cells

Question 25

What molecule is responsible for transporting IgA so it can be effective in the lumen of the gut?

Answer 25

Poly-Ig receptor