Suppressive effect of an Ascaris suum extract on IgE and IgG antibody responses in mice.

1. A suppressed cytotropic and agglutinating antibody response against ovalbumin was induced in mice immunized with this antigen and an Ascaris suum extract. 2. Suppression of IgE antibody production was abolished by administration of cyclophosphamide or X-irradiation before immunization. In contrast, suppression of homocytotropic IgG1 and heterocytotropic IgG2a antibody responses was considerably resistant to the same treatments. 3. The low levels of IgG agglutinating antibodies also remained unchanged after these treatments. 4. These results indicate that distinct regulatory mechanisms are the targets of suppression induced by A. suum extract in IgE and IgG responses.