Rodent IgE-binding factor genes are members of an endogenous, retrovirus-like gene family

Synthesis of IgE by B lymphocytes can be regulated by soluble lymphocyte factors which have affinity for the Fc region of IgE (IgE-binding factors). In previous studies, we identified cDNA clones encoding rodent IgE-binding factors by direct expression in transfected mammalian cells. Here we show that IgE-binding factor cDNA clone 8.3 is a member of the endogenous, retrovirus-like intracisternal A-particle gene family of the mouse. This conclusion is supported by blot hybridization, DNA sequence comparisons, heteroduplex analysis, and immunochemical cross-reactivity of the encoded proteins. The results identify a member of this highly reiterated gene family with a role in regulation of the allergic immune response.