Mucosal Immunity

Question 1

Types of mucosal surface

Answer 1

• Type 1 (simple epi)

- Type 2 (stratified squamous epi)

Question 2

Types of MALT

Answer 2

• GALT
• BALT
• NALT
• genitourinary tract

Question 3

Challenges of MALT

Answer 3

• most frequent portal of entry for harmful substances
• has to mount effective response against vast number of pathogens
• membranes must allow for nutrient absorption
• must remain hypo-responsive to array of harmless substances

Question 4

Examples of unnecessary response leading to disease

Answer 4

• Celiac disease (wheat gluten)
• IBD (commensals)
• asthma (allergens)

Question 5

Organised lymphoid tissue in the gut

Answer 5

Peyers patches

Question 6

Describe Peyer’s patches

Answer 6

• in sub-mucosal layer of intestinal wall

- B cell- follicles and T cell dependent areas

Question 7

Describe M cells

Answer 7

• specialized to transport microorganisms to GALT
• appear as sunken area on epi surface
• no villi
• portal of entry for many pathogens

Question 8

Main humoral mediators of specific mucosal immunity

Answer 8

• secretory IgA

- secretory IgM

Question 9

Describe sIgA activity

Answer 9

• plasma cells release pIgA
• mucosal epi cells have pIgR receptor
• transport of IgA across epi and cleavage of pIgR
• acts by blocking epi receptors and hindering attachment to epic ells

Question 10

Clinical manifestation of IgA deficiency

Answer 10

• increased incidence of infection
• upper and lower resp tract
• GIT
• higher incidence of AI disease
• higher incidence of allergic disease
• higher incidence of celiac disease

Question 11

Describe Intraepithelial lymphocytes (IELs)

Answer 11

• lymphocytes interspersed between columnar epi cells of the villi in the intestine
• most are CD8 T cells
• first line of defense
• secrete large amounts of cytokines (IFNy and TNFa)
• modulate kinetics of epi cell renewal
• regulatory role in tolerance to dietary antigens

Question 12

Describe T cell homing to the gut

Answer 12

• naive T cells carry CCR7 and L-selectin which direct entry into Peyer’s patch
• in T cell area, encounter antigen that has been transported into tissue by M cells and presented by DCs
• lose L-selectin and acquire CCR9
• travel through lymph node, enter blood and home back to gut

Question 13

How does Salmonella typhimurium penetrate the gut epi?

Answer 13

• adheres to and enters M cells (kills them)
• bind fimbriae of epi cells
• infect protruding dendrites

Question 14

How does Shigella flexneri act?

Answer 14

• bacterial dysentry
• binds M cells
• translocated beneath gut epi
• infect intestical epi cells from basal surface and released into cytoplasm
• LPS on shigella activates NF-kB pathway to recruit neutrophils

Question 15

2 diseases of IBD

Answer 15

• Crohn’s disease (Th1 in small intestine and colon, deep patchy inflammation)
• Ulcerative colitis (Th2 in colon, continuous inflammation)