Page 1471 - Veterinary Immunology, 10th Edition

Both adult and larval amphibians have circulating B and T cells
VetBooks.ir that probably originate in the ventral cavity bodies or the liver.

About 80% of circulating lymphocytes carry surface IgM. Frogs also
possess NK-like and T cytotoxic–like killer cells.

Anuran amphibians have up to five immunoglobulin isotypes:
IgM, IgD, IgX, IgY, and IgF. The two most important are IgM and
IgY. They are the least evolved vertebrates to show isotype
switching.

IgM and IgY: Frogs immunized with bacteria or foreign
erythrocytes will produce only IgM. Bacteriophages or soluble
foreign proteins induce both IgM and IgY. The IgY takes up to 1
month to appear, and its level is very low. Amphibians do not

mount a secondary response to erythrocytes and bacteria, but
memory develops in response to the antigens that stimulate an IgY
response. Studies of immunological memory are complicated by the
fact that antigens may persist in the circulation for several months

after injection.
IgX: IgX is orthologous to avian IgA. It is produced in response to
oral immunization. (Fig. 43.9). Anurans have secretory
immunoglobulins in bile and the intestine (but not in skin mucus).

These consist of IgM and IgX but not IgY.

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