L13- Mucosal Immunity Flashcards
What are the approximate surface areas of skin and mucosa?
Skin= 1.8 m2 Mucosa= 400 m2
Why is the mucosal immune system so big?
The gut/alveoli is only lined by a single layer of epithelium which is a weak barrier from the outside world.
Epithelium of gut/alveoli is moist (for easier diffusion) which is more susceptible to bacterial growth.
What are specialised features of the mucosal immune system?
Mucus- trap and remove pathogens
Small microbicidal molecules- defensins that kill pathogens
Mechanical - peristalsis in the gut prevents pathogen build up, cilia in bronchi
Mucosal B cell responses with specialised IgA and IgM
Mucosal T cells
Oral tolerance so immune system doesn’t respond to food
Routes of migration homing receptors/addressins
What is Follicle Associated Epithelium?
A site where antigens are actively recruited in. Contains specialised M cells that sample the particulate contents of the gut lumen and transport them to the lymphoid tissue below.
What do dendritic cells do in the GALT?
They generate retinoic acid from Vitamin A by activity of enzyme RALDH.
Binding of retinoic acid to retinoic acid receptors on lymphocytes induces mucosal honing receptors.
This allows cells to migrate from site of induction to site of expression (imprinting).
What are the honing receptors?
Integrin (alpha4beta7) allows binding to MADCAM1 on endothelium- movement into tissues
CCR9 (chemokine receptor) creates chemokine gradient once cells are inside tissues to help them migrate to their destinations
How does IgA enter the gut lumen?
IgA binds to poly-Ig receptor on cells of lamina propria via J chain
Active transcytosis of IgA into epithelial cell and deposit into gut lumen
What are the intestinal T cells?
Peyers patch T cells (CD4)
Lamina propria T cells (CD4)- generated in GALT, most make interferon gamma, alphabeta T cell receptor
Intraepithelial lymphocytes (CD8)- stable, doesnt produce cytokines, NKG2D receptor
