Page 675 - Veterinary Immunology, 10th Edition

Retinoic acid, the active metabolite of vitamin A, is a central
VetBooks.ir regulator of mucosal immunity. In association with TGF-β, it

enhances T cell proliferation and cytotoxicity and is especially
important in promoting Th2 and Treg differentiation and in the
+
homing of IgA B cells to mucosal surfaces (Chapter 22). It is
essential for maintaining the stability of Th1 cells and prevents their
transition to Th17 cells. Retinoic acid normally suppresses Th17
responses and favors tolerance to food antigens.

Interleukin-22.

IL-22 is produced by Th17 cells, activated T cells, and ILC3s in
response to IL-23. IL-22 reduces the absorption of food allergens.
IL-22-producing ILC3s are present in normal intestinal tissues,

especially in cryptopatches (Chapter 12). The IL-22 acts on nearby
Paneth cells to produce antimicrobial peptides (lipocalin-2 and
calprotectin). IL-22 acts on cells of the skin and the digestive and
respiratory systems to increase expression of several β-defensins
and promotes innate immunity and repair in these tissues. It

promotes enterocyte growth and survival.

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