ALLERGEN-DIRECTED EXPRESSION OF FC-RECEPTORS FOR IGE (CD23) ON HUMAN LYMPHOCYTES-T IS MODULATED BY INTERLEUKIN-4 AND INTERFERON-GAMMA

T lymphocytes bearing Fc receptors (FcR) for immunoglobulins are known to have immunoglobulin class‐specific regulatory functions. Here we report that expression on T cells of the low‐affinity FcR for IgE (FcϵRII/CD23) is preferentially induced by stimulation with antigens that cause an IgE response. T cells from eight patientsallergic to the hemoglobin of Chironomus thummi thummi mosquito larvae (CHIT I) were analyzed for reactivity with the anti‐FcERII/CD23 monoclonal antibody (mAb)M‐L25 under various conditions. No FcϵRII/CD23+ T cells were observed among freshly isolated, resting peripheral blood mononuclear cells (PBMC). Stimulation of PBMC with CHIT I, however, induced a marked although transient FcϵRII/CD23 expression on a large portion of the allergen‐activated T lymphocytes. It reached a maximum of 37.2 ± 4.6% FcϵRII/CD23+ T cell blasts on day 5 of culture. The selectivity of this expression became evident when compared to non‐allergenic control antigens: after stimulation of PBMC with tetanus toxoid or purified protein derivative from tuberculin a maximum of 4.6% ± 1.4% and 4.2% ± 1.1% T cell blasts was found to express FcϵRII/CD23, respectively. Activation by an anti‐CD3 mAb was insufficient to induce FcϵRII/CD23 on T cells. The allergen‐stimulated FcϵRII/CD23+ T cells exclusively belonged to the CD4+CD29+ helper inducer T cell subset. Using a cDNA probe coding for the B cell FcϵRII/CD23, Northern blot analysis revealed a 1.7‐kb FcϵRII/CD23 mRNA in extracts of highly purified allergen‐stimulated T cells. It was of the same size as FcϵRII/CD23 mRNA of the lymphoblastoid B cell line WI‐L2. Of several cytokines tested [interleukin (IL) 1 to IL 6, interferon‐γ (IFN‐γ), tumor necrosis factor‐α] only IL 4 and IFN‐γ significantly modified allergen‐induced FcϵRII/CD23 expression onT cells. The latter was enhanced nearly twofold in the presence of IL 4, and was almost completely abrogated by IFN‐γ. IL 4, however, could not increase the number of FcϵRII/CD23+ T lymphocytes either alone or in combination with an anti‐CD3 mAb. Taken together, the selective induction of FcϵRII/CD23 onT cells by allergen and its inclusion in the regulatory network of cytokines point to an important role of FcϵRII/CD23+ T lymphocytes in the human IgE response. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim