Page 718 - Veterinary Immunology, 10th Edition

motility may be sufficient to force the parasite to disengage—a
VetBooks.ir phenomenon called “self-cure” (Chapter 28).

Thus IgA and IgE work in concert. IgA normally is the first line of
defense, and IgE serves as a backup system. If IgA production is

defective, the IgE response may be triggered to excess. As a result,
low levels of IgA result in increased IgE production and the
development of allergic responses to food and inhaled antigens.

Immunoglobulin G
In ruminants (especially cattle), IgG1, not IgA, is the major

secretory immunoglobulin in colostrum and milk. This is due to
selective transfer from the bloodstream into the mammary gland.
On other body surfaces in ruminants, however, IgA remains the

predominant immunoglobulin, although IgG1 is also present. IgG2
is also transferred into the intestine and saliva in ruminants. IgG
may be of greater protective significance in the respiratory tract
than in the intestine because there it is less likely to be degraded by
proteases.

718