Page 708 - Veterinary Immunology, 10th Edition

FIG. 22.9 When stimulated by antigen, IgA-producing B cells are
VetBooks.ir eventually settle on other surfaces, such as the lung, the mammary
produced in inductive sites, such as the Peyer's patches. They then
leave the intestine and circulate in the bloodstream. They all

gland, and other regions of the gastrointestinal tract effector sites,
reflecting the existence of a common mucosal immune system. This
transfer of antibody-producing cells in the mammary gland ensures
that milk contains IgA antibodies directed against intestinal
pathogens.

T Cells

Both α/β and γ/δ T cells are found in the intestinal wall but in two
very different locations. Thus α/β T cells are mainly scattered

throughout the lamina propria and in Peyer's patches. γ/δ T cells, in
contrast, are situated between enterocytes immediately below the
mucosal surface, where they are known as intraepithelial
lymphocytes (IELs) (Fig. 22.10). Their location suggests that they

play an early role in the defense of the mucosa. IELs regulate host-
microbial interactions at the intestinal mucosal surface and are
critical components in preventing invasion by the commensal
microbiota. IEL function is in turn regulated by many different

cytokines including IL-2, -7, -15, and TGF-β.

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