FUNCTIONAL-SIGNIFICANCE OF CD23 ON CD23-TRANSFECTED TH2 CLONE

CD23, a low-affinity IgE Fc receptor, is not displayed on most resting T cells but its expression has been shown to be transiently induced i n vivo and in vitro on some CD4(+) T cells [1-4] and in vivo on CD8(+) T cells by IgE-secreting hybridoma tumors [5]. To investigate the fun ctional role of CD23 on T cells, we inserted a CD23 construct into an expression vector driven by a CD2 promoter and transfected it into a m urine Th2 clone D10.G4.1 (D10). We stimulated the transfected D10 cell s (D10.3M.24) with anti-TCR antibody in the presence or absence of IgE , and measured IL-4, IL-5 and IL-6 production in the culture supernata nts. Activation of D10.3M.24 cells by anti-TCR antibody induced greate r levels of IL-4, IL-5 and IL-6 production, when the TCR and CD23 were co-crosslinked by TNP anti-TCR and IgE anti-TNP antibodies. IgG anti- TNP antibody did not enhance lymphokine production by D10.3M.24 cells. The enhanced lymphokine production by IgE was blocked by monoclonal a nti-CD23 antibody. IgE anti-TNP antibody did not enhance lymphokine pr oduction by the wild-type D10 cells induced by TNP anti-TCR antibody. These studies show that when co-crosslinked with the TCR, CD23 can mod ulate the lymphokine production in activated Th2 cells. Since CD23 bin ds to IgE and also binds to CD21 [6], a complement receptor commonly e xpressed on B cells, T-cell CD23 could play an immunoregulatory role d uring cognate T-B cell interaction and during IgE antibody responses.