Page 671 - Veterinary Immunology, 10th Edition

VetBooks.ir

FIG. 21.9 The countervailing activities of Tregs and Th17 cells
require a balanced microbiota to maintain health.

Intestinal helper T cell phenotypes are “plastic,” and precursor
cells can differentiate into either Treg or Th17 cells, while Th17 cells

may further differentiate into Th1 cells. This differentiation is
regulated by signals from the microbiota. In effect the microbiota
program the T cell system to optimize its function. Additionally,

helper T cell differentiation is determined by cytokines. For
example, the development of both Tregs and Th17 cells are
promoted by TGF-β. Treg cells require TGF-β plus retinoic acid and
IL-2, whereas Th17 cells require TGF-β plus IL-6 and IL-23. The
major transcription factors used by Tregs and Th17 are FoxP3 and

RORγt respectively, and these are co-expressed in naïve and
+
effector CD4 cells.

Treg cells.

671