Page 622 - Veterinary Immunology, 10th Edition

VetBooks.ir Antibody Regulation of Immune

Responses

As a result of negative feedback, antibodies generally suppress B
cell responses. IgG antibodies tend to suppress the production of
both IgM and IgG, whereas IgM antibodies suppress only the
synthesis of IgM. Specific antibodies tend to suppress a specific

immune response better than non-specific immunoglobulins.
This negative effect of antibodies on B cell functions is mediated
through the inhibitory B cell receptor CD32b (FcγRIIb). In diseases
where immunoglobulin levels are abnormally high, as in patients

with myelomas (Chapter 15), this feedback depresses normal
antibody synthesis, and patients become susceptible to infections. A
similar phenomenon occurs in newborn animals that acquire
antibodies from their mother. The presence of maternal antibodies,

while conferring protection, inhibits immunoglobulin synthesis and
so prevents the successful vaccination of newborn animals (Fig.
20.8).

FIG. 20.8 The presence of maternal antibody in a newborn animal
effectively delays the onset of immunoglobulin synthesis through a
negative feedback process.

Serum IgG levels are also regulated through the neonatal
immunoglobulin receptor (FcRn) (see Fig. 23.6). Despite its name, it
is present throughout life and is widely distributed on endothelial

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