The isotypes of antibody responsible for the 'late' passive transfer of immunity in rats vaccinated with highly irradiated cercariae.

The role of different antibody isotypes in the transfer of protection with serum from rats vaccinated with irradiated cercariae were investigated by immunoadsorption of IgG, IgG2a and IgG2c, and by heating at 56 degrees C to remove IgE. Only depletion of IgG2a reduced the levels of vaccine-induced immunity transferred, whereas immunity transferred by infection serum was reduced by both IgG2a and IgE depletion. It was also shown that exposure to irradiated parasites did not lead to either specific or non-specific induction of an IgE response. The successful passive-transfer experiments using serum from non-resistant 25 week-infected rats into recipient animals demonstrated that the waning of resistance observed in 25 week-infected rats was not due to a failure of the humoral response to protective antigens.