Page 633 - Veterinary Immunology, 10th Edition

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FIG. 20.14 The production of Th17 cells. The original
differentiation signal comes from IL-23. This signal is amplified by
IL-21, IL-6 and TGF-β .

Dendritic cells and macrophages activated by microbial PAMPs
through TLR2 secrete IL-23 (Box 20.1). IL-23 promotes the

activation of Th17 cells. Th17 cells secrete IL-17A, IL-17F, IL-21, and
IL-22 (Fig. 20.15). IFN-γ suppresses the development of Th17 cells
and inhibits IL-17-mediated inflammation.

Box 20.1

Interleukin-23

IL-23 is closely related to IL-12. Both are heterodimers consisting of
an identical p40 subunit and a second smaller subunit, IL-23p19 or

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