Presence of an antigenic determinant common to rat IgE-potentiating factor, IgE-suppressive factor, and Fc(ε), receptors on T and B lymphocytes

Polyclonal antibodies against purified IgE-potentiating factor were prepared in guinea pigs, and mouse monoclonal antibodies were prepared against inactive IgE-binding factor from a T cell hybridoma. The polyclonal antibodies and two of the monoclonal antibodies bound the IgE-potentiating factor, the IgE suppressive factor, and the inactive IgE-binding factor. The results indicate that the three IgE-binding factor molecules share a common antigenic determinant. The polyclonal antibodies and the monoclonal antibody bound intracellular IgE-binding factors that did not have affinity for either lentil lectin or peanut agglutinin, which suggests that the antibodies were directed against the peptide portion of IgE-binding factors. Pretreatment of Fc(ε)R⁺ T hybridoma cells and Fc(ε)R⁺ B cells with either the monoclonal or the polyclonal anti-IgE-binding factor (anti-IgE-bF) antibody prevented rosette formation of the cells with IgE-coated erythrocytes, whereas the same treatment failed to affect rosette formation of FC(γ)R⁺ cells with IgG-coated erythrocytes. Specific binding of the guinea pig anti-IgE-bF antibodies to Fc(ε)R on both B and T cells was confirmed by immunofluorescence. The results indicate that Fc(ε)R on B and T cells share a common antigenic determinant with IgE-binding factors. The F(ab')₂ fragments of the guinea pig anti-IgE-bF induced the expression of Fc(ε)R on Fc(γ)R⁺ lymphocytes and the formation of IgE-binding factors. The capacities of not only IgE, but also anti-IgE-bF, to induce both Fc(ε)R expression and IgE-binding factor formation indicate that Fc(ε)R on lymphocytes, rather than IgE, transmit the signal for the formation of IgE-binding molecules.