Effects of cyclophosphamide treatment and gamma irradiation of SJL mice on the IgE antibody response and the nature of IgE-binding factors.

Immunization with alum-absorbed ovalbumin (OA) failed to induce IgE antibody responses in SJL mice, while mice pretreated with either cyclophosphamide (CY) or gamma-irradiation prior to immunization transiently formed IgE antibodies. Spleen cells of OA-primed SJL mice formed IgE-suppressive factors upon incubation with OA. In contrast, spleen cells of the CY-treated or irradiated mice formed IgE-potentiating factors. It was found that CY treatment diminished the formation of glycosylation inhibiting factor (GIF) and enhanced the formation of glycosylation enhancing factor (GEF). The results suggest that the enhancement of the IgE antibody response by CY treatment is due not only to elimination of suppressor T cells but also to the activation of GEF-forming lymphocytes.