Biologically active molecules regulating the IgE antibody system: biochemical and biological comparisons of suppressive factor of allergy (SFA) and enhancing factor of allergy (EFA).
Studies in recent years directed at unraveling the complex regulatory mechanisms controlling IgE antibody production have demonstrated the existence of soluble factors that exert selective regulatory effects on the IgE antibody system. In addition, the demonstration of IgE-specific Fc receptors (FcR epsilon) on B and T lymphocytes, especially after exposure to high concentrations of IgE either in vivo or in vitro, has provided increasingly strong indications of an important role for such cells in the overall control of the IgE system. In our own laboratory, we have been studying soluble regulatory factors known as suppressive factor of allergy (SFA) and enhancing factor of allergy (EFA), which were initially identified by their selective, and opposing, regulatory effects on in vivo IgE responses in inbred mice. More recently, in an in vitro system in which it is possible to induce the de novo expression of FcR epsilon on lymphocytes cultured in the presence of monoclonal IgE, we reported that concomitant exposure of such cultured cells to SFA selectively blocked the induction of FcR epsilon expression. In the present study, we have extended these investigations by making a direct comparison between certain biological properties and biochemical characteristics of SFA and EFA. We found that SFA and EFA can be distinguished biochemically on the basis of size, SFA falling in the range of 30,000 daltons or so, and EFA falling in the range of 15,000 daltons. In examining their biological properties, we unexpectedly found that although SFA-enriched and EFA-enriched fractions exert dramatically distinct biological effects on in vivo IgE antibody synthesis (as implied by their names), the two respective active fractions are totally indistinguishable in their inhibitory effects on IgE-mediated induction of FcR epsilon + lymphocytes in vitro when intact spleen cell populations are exposed to monoclonal IgE. That the active entities in SFA and EFA responsible for inhibition of FcR epsilon induction do not exhibit IgE-binding properties was shown by the fact that adsorption on IgE-coupled affinity columns had no appreciable effect on their inhibitory capacities. This distinguishes these molecules from the IgE-binding factors described by Ishizaka and colleagues. Moreover, as previously documented for SFA, we found that EFA neither possesses immunoglobulinlike determinants nor binds to other immunoglobulin class molecules. Finally, chromatographically fractionated EFA was shown to exert its enhancing activity on in vivo IgE antibody production across strain barriers, thereby ruling out any genetic restriction on its functional capacity. A similar absence of genetic
D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000096:biosynthesis; D007073:Immunoglobulin E / Q000096:biosynthesis*; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000276:immunology; D051379:Mice; D011961:Receptors, Fc / Q000096:biosynthesis; D017455:Receptors, IgE; D013491:Suppressor Factors, Immunologic / Q000276:immunology* / Q000302:isolation & purification / Q000494:pharmacology
D000944:Antigens, Differentiation, B-Lymphocyte; D011961:Receptors, Fc; D017455:Receptors, IgE; D013491:Suppressor Factors, Immunologic; D007073:Immunoglobulin E