Polymorphonuclear neutrophils enhance anti-CD3-induced T cell activation: The role of polymorphonuclear FC-receptors

Abstract We investigated the effect of Polymorphonuclear neutrophils (PMN) on anti-CD3 mAb (OKT3 and anti-Leu4)-mediated T cell activation. In the absence of monocytes, purified E-rosette-positive cells (further referred to as “T cells”) require either solid-phase bound anti-CD3 or the combination of both a high concentration of soluble anti-CD3 and exogenous recombinant interleukin 2 (rIL-2) to proliferate. PMN cannot sustain T cell proliferation with soluble anti-CD3, but they markedly boost proliferation in the presence of soluble anti-CD3 and rIL-2. When PMN were added to T cell cultures stimulated with anti-CD3, this resulted in IL-2 receptor (IL-2R) expression and CD3 modulation. The mechanism of enhancement of anti-CD3-induced IL-2-responsiveness by PMN was further analyzed. A cellular T cell-PMN interaction was found to play a critical role and this was mediated through PMN Fc receptors (FcR). PMN bear two types of low-affinity FcR (FcRII and FcRIII). FcRII is known to bind mIgG1 (e.g., anti-Leu4) and FcRIII binds mIgG2a (e.g., OKT3). FcR involvement was demonstrated by two observations. Anti-FcRII mAb IV.3 inhibited the PMN signal for T cell activation with anti-Leu4. PMN bearing the second variant of FcRII which is unable to bind mIgG1 failed to promote anti-Leu4/IL-2-mediated T cell proliferation. Thus, PMN potentiate T cell responsiveness to IL-2 in the presence of anti-CD3 mAb and this potentiation by PMN requires interaction of anti-CD3 with PMN-FcR.