MATURE POLYMORPHONUCLEAR LEUKOCYTES EXPRESS HIGH-AFFINITY RECEPTORS FOR IGG (FC-GAMMA-RI) AFTER STIMULATION WITH GRANULOCYTE-COLONY-STIMULATING FACTOR (G-CSF)

The high-affinity receptor for the constant region of immunoglobulin G IgG (Fc gamma RI; CD64) is virtually undetectable on mature polymorph onuclear neutrophils (PMNs) in healthy individuals but is expressed on PMNs in patients with certain infections and in patients treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF). Th e induction of Fc gamma RI by rhG-CSF has previously been reported to result from effects on immature granulocyte progenitors. To evaluate t he G-CSF effect on mature PMNs, we studied the correlation between G-C SF plasma concentration and expression of Fc gamma RI on PMNs in vivo as well as the effect of G-CSF on Fc gamma RI expression on mature PMN s in vitro. Fc gamma RI expression on PMNs correlated (R = 0.79; p < . 001) with plasma concentrations of endogenous or recombinant G-CSF in healthy volunteers and in patients undergoing high-dose chemotherapy a nd autologous bone marrow transplantation. PMNs exhibited a unimodal d istribution for elevated Fc gamma RI expression, suggesting that G-CSF induced increased expression of Fc gamma RI on mature as well as on i mmature PMNs. In vitro, incubation of mature PMNs with G-CSF induced m RNA for Fc gamma RI, Significant Fc gamma RI surface expression was in duced in a time- and dose-dependent manner. Thus, G-CSF can act on mat ure PMNs to increase Fc gamma RI expression and may be useful for stim ulating antibody mediated immune functions of PMNs in vivo.