cDNA clones encoding IgE-binding factors from a rat-mouse T-cell hybridoma.

Abstract
C[complementary]DNA clones encoding rodent IgE-binding factors (IgE-BF) were isolated from cDNA libraries of a rat-mouse T hybridoma that secretes IgE-suppressive factor (IGE-SF) upon incubation with rat IgE. COS7 [chicken] cells transfected with 2 of the cDNA expressed IgE-BF, which selectively potentiate an in vitro IgE response. IgE-BF expressed in COS7 cells are glycoproteins of .apprxeq. 60 and .apprxeq. 11 kDa [kilodalton]. DNA sequence analysis of an IgE-BF cDNA revealed a 556-amino acid (62 kDa) protein coding region. Evidently, IgE-potentiating and IgE-suppressive factors share common precursor polypeptides and the 11-kDa IgE-BF is derived from a 6-kDa precursor.