Page 717 - Veterinary Immunology, 10th Edition

This is mediated by IgE. Cells producing IgE are mainly found
VetBooks.ir under epithelial surfaces rather than in the lymph nodes or spleen.

IgE binds to mast cell Fc receptors in the mucosa of the intestine
and respiratory tract, and under the skin. If invading organisms

evade the IgA and gain access to the tissues, IgE-mediated
inflammation will be triggered (Fig. 22.15). These responses involve
rapid degranulation of mast cells and the release of their
inflammatory mediators into the surrounding tissues. As described

in Chapter 29, the mast cell contents cause acute inflammation,
increase the permeability of small blood vessels, and promote fluid
leakage between enterocytes, leading to the outflow of mucus
containing large quantities of IgG.

FIG. 22.15 The IgE response in the intestinal wall. Antigen
reaches IgE-sensitized mast cells to cause their degranulation. As a
result of this, vasoactive factors are released. These cause
increased vascular permeability and exudation of serum IgG
antibodies.

This process occurs, for example, when parasitic worms invade
the intestinal mucosa. IgA has little effect on these invaders, so they
have no difficulty in burrowing into the superficial layers of the

mucosa. When sensitized mast cells encounter parasite antigens,
however, the release of vasoactive molecules, together with the
intense local inflammation, changes in blood flow, and intestinal

717