Mucosal immunity

Question 1

What are some innate immune defences?

Answer 1

Peristaltic, secretion of acid, mucous layer, enterocytes, macrophages and dendritic cells

Question 2

What is the function of Paneth cells?

Answer 2

To produce antimicrobial peptides and proteins (defensins) such as alpha-defensins

Question 3

Goblet cells function

Answer 3

• nutrient digestion and the secretion of mucins

Question 4

How do lymphocytes return to the intestine?

Answer 4

Dendritic cells imprint addressin on lymphocytes
: alpha-7-beta-4 integrin binds to MAdCAM-1 on endothelial cells, chemokine receptor 9 binds to CCL25

Question 5

Production of secretory IgA in epithelial cells

Answer 5

Dimeric IgA binds to plg receptor on basolateral face of epithelial cell
Taken in by endocytosis
Transcytosis to apical face of epithelial cell
Part of receptor (secretory component) stays bonded
Protects IgA from degradation and helps it anchor in the mucus

Question 6

Secretory IgA

Answer 6

• Does not activate complement cascade, weak opsonin (binds to foreign particles and marks them for phagocytosis)
• Block epithelial attachment
• Block toxin attachment
• Intracellular neutralisation of organisms that invade the mucosal epithelia

Question 7

Peyer’s patches

Answer 7

site of lymphocyte activation. Microfold cells line the patch, sample lumen and deliver antigens into patch

Question 8

Predominant lymphocyte pathways in mucosal immunity

Answer 8

Predominant t cells are Treg (cells that can repress the activity of other cells) or Th2 < aiming to induce a non inflammatory immune response

Th2 pushes a bias of B cell isotype switching to secretory IgA

Question 9

M cells

Answer 9

derived from enterocytes, no microvilli, lack glycocalyx, does not express MHC-II