CTLA4Fcε, a novel soluble fusion protein that binds B7 molecules and the IgE receptors, and reduces human in vitro soluble CD23 production and lymphocyte proliferation
Abstract
Immunoglobulin E-mediated allergy and certain autoimmune diseases are characterized by the presence of a T helper type 2 (Th2) immune response and allergen-specific or self-reactive IgE. Soluble CD23 (sCD23) is a B-cell factor that fosters IgE class-switching and synthesis, suggesting that sCD23 may be a therapeutic target for these pathologies. We produced a recombinant protein, CTLA4Fcε, by fusing the ectodomain of the immunoregulatory molecule cytotoxic T-lymphocyte antigen 4 (CTLA-4) with a fragment of the IgE H-chain constant region. In SDS-PAGE/inmunoblot analyses, CTLA4Fcε appeared as a 70,000 MW polypeptide that forms homodimers. Flow cytometry showed that CTLA4Fcε binds to IgE receptors FcεRI and FcεRII/CD23, as well as to CTLA-4 counter-receptors CD80 and CD86. Binding of CTLA4Fcε to FcεRII/CD23 appeared stronger than that of IgE. Since the cells used to study CD23 binding express CD80 and CD86, simultaneous binding of CTLA4Fcε to CD23 and CD80/CD86 seems to occur and would explain this difference. As measured by a human CD23-specific ELISA, CTLA4Fcε - but not IgE - induced a concentration-dependent reduction of sCD23 in culture supernatants of RPMI-8866 cells. Our results suggest that the simultaneous binding of CTLA...Continue Reading
References
The anti-inflammatory effects of omalizumab confirm the central role of IgE in allergic inflammation
Recombinant polymeric IgG anti-Rh: a novel strategy for development of direct agglutinating reagents
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