Page 713 - Veterinary Immunology, 10th Edition

CD154 interactions, trigger B cell IgA production in the absence of
VetBooks.ir antigen. Enterocytes and intraepithelial lymphocytes also produce

APRIL and promote B cell differentiation. B cells that require both
antigen and Th2 cells to make the switch to IgA are stimulated by

TGF-β (Fig. 22.12). Other Th2 cytokines that promote this switch
include IL-4, IL-5, IL-6, and even IL-10. The IgA response is
relatively slow to develop and has a very high threshold for
9
induction (10 bacteria). When boosted, the IgA response does not
increase exponentially but rather in an additive manner. The
plasma cells that synthesize IgA have other unique properties in
that they also produce TNF-α and nitric oxide synthase and thus
share some properties with monocytes. These additional products

appear to contribute to the defenses of the intestine.

FIG. 22.12 The control of IgA production. Multiple Th2 cytokines,
especially TGF-β, are primarily responsible for the IgM-to-IgA
switch. Co-stimulation is provided by BAFF and APRIL from
epithelial cells and dendritic cells as well as CD40-CD154
interactions.

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