Formation of IgE-binding factors by rat T lymphocytes. I. Induction of IgE-binding factors by poly I:C and interferon

Rat serum obtained 8 to 18 hr after an i.p. injection of poly I:C contained IgE-binding factors, which can be detected by the inhibition of rosette formation of FcεR(+) cells with IgE-coated erythrocytes. Incubation of normal rat spleen cells with 1 μg/ml poly I:C resulted in the formation of IGE-binding factors. Approximately one-half of the IgE-binding factors in the culture supernatant were IgE-potentiating factors, which have affinity for concanavalin A (Con A), whereas the remaining half of the factors were IgE-suppressive factors with no affinity for the lectin. Culture supernatants of poly I:C-stimulated spleen cells as well as the serum of polyI:C treated rats contained not only IgE-binding factors but also soluble factors that induce normal lymphocytes to form IgE-binding factors. It was found that poly I:C-stimulated splenic adherent cells and peritoneal macrophages formed soluble factors, which in turn induced T lymphcytes to express FcεR and to form IgE-binding factors. The inducers derived from poly I:C-stimulated cells failed to augment the expression of FcεR on B cells. The soluble factors could induce the formation of both IgE-potentiating factors and IgE-suppressive factors. Upon incubation with the inducers, 10 μg/ml Con A-activated cells formed IgE-potentiating factors; 1 μg/ml Con A-activated cells formed IgE-suppressive factors. The inducers had affinity for polyuridylic acid and blue dextran Sepharose, and could be recovered from the beads by elution with 1 M NaCl. It was also found that supernatant of mouse spleen cells co-cultured with virus-infected Hela cells induced normal rat lymphocytes to form IgE-binding factors. The inducers in the culture supernatants were neutralized by a minute dose of antibodies specific for mouse type 1 interferon, indicating that mouse interferon can induce the formation of IgE-binding factors.