Induction of secondary IgE antibody response in rats immunized with X-irradiated metacercariae of Paragonimus ohirai.

Rats reinfected with Paragonimus ohirai (P.o.) elicited little secondary IgE response to adult P.o. antigen. In contrast, rats immunized with X-irradiated (2-10 krad) metacercariae elicited not only a marked primary IgE response comparable to that in normally infected rats, but also a marked secondary IgE response after challenge infection. Rats immunized with 2 krad X-irradiated metacercariae yielded a higher secondary IgE response than with 5 or 10 krad irradiated ones, and elicited a secondary response lasting at least 1 year. An IgE response to antigen of newly excysted juvenile parasites (NEJ) was clearly different from the IgE response to adult P.o. antigen. The former IgE response was weak after infection or immunization, but after challenge infection a marked secondary response occurred at a level similar to the IgE response to adult P.o. antigen. The secondary IgE responses to adult P.o. and NEJ antigens were also elicited by reinoculation with X-irradiated metacercariae. Cross-absorption experiments confirmed that there were adult type and NEJ type allergens.