Mucosal Immunity

Question 1

Main mucosal surfaces

Answer 1

• Respiratory, Urogenital and Gastrointestinal
• > large surface areas that are continuously exposed to microorganisms and other antigens
• contain large amounts of lymphoid tissues

Question 2

Two categories of mucosal lymphoid tissues

Answer 2

1. Inductive Sites

2. Effector Sites

Question 3

Inductive Sites of Mucosal Lymphoid Tissue

Answer 3

• mucosal sites where Ag are encountered, processed and immune responses (Humoral-Ab and CMI) are initiated

Question 4

Effector Sites of Mucosal Lymphoid Tissue

Answer 4

• mucosal sites where Antibodies and Cell-mediated responses are carried out
• > where they do their jobs
• Ex of effector site is diffuse lymphoid tissues at mucosal surfaces

Question 5

Peyer’s Patches as an Inductive Site Mechanism

Answer 5

1. M-cells facilitate Antigen transport on the lumen
2. M-cells act as a delivery service and transport antigens from the lumen into the body
3. Antibody class switching occurs in the Peyer’s Patches (inductive site)
4. BUT, the Antibody secretion into the lumen occurs in the villi (effector site)

Question 6

M-cells

Answer 6

• are specialized epithelial cells of follicle-associated epithelium of GI tract.
• Perform rapid uptake and presentation of antigens from microbes to APCs
• > NOT classical antigen presentation (NOT an APC), they are a delivery service (Fed-Ex)

Question 7

Where are effector B and T lymphocytes generated?

Answer 7

• inside induction sites and can then travel to distant sites (effector sites) to carry out their function

Question 8

What happens to the B-cells activated in the inductive sites?

Answer 8

• B-cells activated in the intestine can circulate to many body surfaces including back to the intestinal surface
• B-cells at mucosal surfaces secrete IgA

Question 9

The movement of IgA-secreting B cells from the intestine to where is most important? Why?

Answer 9

• to the mammary gland
• provides a route for intestinal immunity to be transferred through milk to newborns
  -> therefore, oral administration of antigens to pregnant animals will result in the appearance of IgA antibodies in the milk
  –> this causes the intestine of the newborn to be flooded by antibodies directed against internal pathogens
  = PASSIVE IMMUNITY through milk is primarily IgA mediated

Question 10

IgA Acquired Protective mechanism

Answer 10

• acts by immune exclusion of Antigens

Question 11

IgE and IgG

Answer 11

• destroys antigen via immune elimination

Question 12

Where is IgA synthesized and secreted?

Answer 12

• by plasma cells in the intestinal mucosa

Question 13

How does IgA get from the submucosa through the intestinal epithelium?

Answer 13

1. Plasma cells (in the submucosa) secrete IgA as a dimer
2. Dimeric IgA binds to a Poly-Ig receptor on the basal surface of enterocytes (epithelial cells lining the intestinal mucosa)
3. The poly-Ig receptor-IgA complex is endocytosed and transported across the enterocyte