Mucosal Immunity

Question 1

What is the function of the mucosal system?

Answer 1

Distinguish between foreign antigens such as food and commensal bacteria (no response), and pathogenic organisms (respond)


Question 2

What is the function of microfold (M) cells?

Answer 2

They take up antigen on the lumen surface and M cells transport them across the cell and release them at the basal surface where Ag is bound by DCs which activate T cells.

Question 3

How is mucosal immunity activated?

Answer 3

• Ag enters the MALT an is taken and transported across by M cells
• DCs take them up and present them to T cells and they migrate to the mesenteric lymph nodes then enter the lymph then thoracic duct and finally circulation
• Circulating lymphocytes will home and B cells in peripheral tissues become IgA plasma cells at effector sites

Question 4

Will mucosal immunity generate systemic immunity?

Answer 4

Yes, it will generate both types.

Question 5

What is the structure of secretory IgA?

Answer 5

Dimeric

Question 6

Will systemic immunity generate mucosal immunity?

Answer 6

No

Question 7

What is the function of Intraepithelial Lymphocytes (IEL)?

Answer 7

Kill infected epithelial cells by perforin/granzyme and Fas dependent pathways

Question 8

How does salmonella penetrate the epithelium?

Answer 8

Enter and kill the M cells and then infect macrophages and epithelial cells and can also enter via the dendrites of DCs.

Question 9

How is IgA transported across the epithelium?

Answer 9

IgA will bing pIGR on the basal surface of epithelial cells and the complex will be transported to the lumen for release.

Question 10

What are the advantages of mucosal immunization?

Answer 10

Oral Administration

Generates mucosal and systemic immunity

Question 11

What are the disadvantages of mucosal immunization?

Answer 11

Response may be short lived

Difficult to avoid the tolerance barrier

Question 12

How to induce mucosal immunity in the tolerogenic environment?

Answer 12

Inflammation is often required.

Question 13

How do commensals protect against pathogens?

Answer 13

Their colonization prevents pathogenic bacteria from getting a foothold in the gut

Question 14

What is the tolerogenic response?

Answer 14

Response occurs with oral intake of food and commensal bacteria with local IgA and low serum Ab as well as no T cell response or response on re-exposure to Ag.

Question 15

What is the immunogenic response?

Answer 15

IgA is present with local and systemic T cells and on re-exposure there is a memory response