Page 664 - Veterinary Immunology, 10th Edition

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FIG. 21.7 The importance of short-chain fatty acids (SFCAs) in
promoting immunity.

If the intestinal microbiota is altered in such a way that there is
increased production of acetate, then this will activate the
parasympathetic nervous system and promote glucose-stimulated

insulin production. This stimulates production of a hunger
hormone called ghrelin that enhances appetite, leading to increased
food intake and obesity.
Among the intestinal microbiota, some species play a key role in
regulating immune responses. One such group are classified as

Clostridial clusters. Several of these bacteria (Clostridia clusters IV,
XIVa, and XVIII) specifically induce Treg cells and IL-10 production
in the gut. These Clostridia form a thick layer over the epithelium

and enhance the release of transforming growth factor-β (TGF-β)
and indoleamine 2,3-dioxygenase (IDO) from enterocytes (Fig.
21.8). They also promote mucus production by goblet cells.

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