IgE and IgG2a antibody responses are induced by different antigen groups of the nematode Nippostrongylus brasiliensis in rats.

The differences were examined between IgE, IgG1 and IgG2a antibody responses against two kinds of nematode antigens in rats infected with Nippostrongylus brasiliensis. With ELISA studies, remarkable IgE and IgG1 antibody responses were observed against antigens in excretory/secretory products (ES) of N. brasiliensis, whereas the IgG2a antibody response against ES was negligible. On the other hand, antibody response to antigens in an extract of homogenized adult worm (AW) was observed mainly in IgG2a, with little response in IgE or IgG1. Immunohistochemical studies showed that IgE- and IgG1-binding antigens were localized almost exclusively in the subventral glands, a secretory apparatus in N. brasiliensis, while IgG2a-binding antigens were found mainly in the nematode wall along the body cavity. Immunoblot analysis revealed that the major IgE- and IgG1-binding molecules in ES were identical. On the other hand, some, but not all, of the major IgG2a-binding molecules in AW were different from the IgE/IgG1-binding molecules in ES. The findings suggest that the IgE/IgG1 and IgG2a antibody responses in N. brasiliensis-infected rats are induced by different groups of nematode antigens. Thus, it is presumed that the production of each class of antibody might be dependent, at least in part, on the nature of the antigen or antigen-linked molecules.