CD23/FC-EPSILON-RII EXPRESSION ON PHYTOHEMAGGLUTININ-A-ACTIVATED OR PHORBOL-(12)MYRISTATE-(13)ACETATE-CA2+-ACTIVATED HUMAN TONSIL T-CELLS

The low-affinity Fc receptor for IgE, CD23/FcepsilonRII, has been expressed in T cell lines and pathologic T cells, but its presence on normal human T cells is still debated. We studied the expression of CD23/FcepsilonRII on purified T cells from normal peripheral blood mononuclear cells (PBMC) or tonsil T cells stimulated with 10 mug/ml phytohemagglutinin A (PHA) or phorbol-12myristate-13-acetate PMA) Ca2+. Using two-dimensional flow cytometry, the tonsil T-cell-enriched population showed > 10% of CD23/FcepsilonRII expression when coexpressed with the CD3 antigen. CD4+ T cells appear to be principally involved in the expression of CD23/FcepsilonRII, although we were unable to detect a clear expression of CD23/FcepsilonRII in PBMC that were activated with either PHA or PMA Ca2+. PHA stimulation resulted in the release of IgE binding factor (fgEBF). The induction of CD23/FcepsilonRII expression in PHA- and PMA-Ca2+-activated T cells was enhanced by IL-4, but not by IgE or IL-6. IL-4 also augmented the PHA- and PMA-Ca2+-induced release of IgEBF. The addition of supernatant from the Epstein-Barr virus (EBV)-infected cell line to PHA-or PMA-Ca2+-stimulated tonsil T cells did not increase CD23/FcepsilonRII expression. The expression of CD23/FcepsilonRII mRNA was detected in RNA prepared from a tonsil T-cell-enriched population by Northern blot analysis.