Effect of rIFN-gamma on antibody-mediated cytotoxicity via human monocyte IgG Fc receptor II (CD32).

Human monocytes and macrophages express an isoform of IgG Fc receptor II (Fc gamma RII), Fc gamma RIIa. Two allotypic variants of this receptor could be distinguished with respect to their ability to bind murine (m)IgG1 complexes either strongly or weakly, defined as high-responder (HR) and low-responder (LR), respectively. We investigated the effect of recombinant (r)IFN-gamma on the ability of freshly isolated monocytes, and those cultured for 40 h and 9 days, to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). Using human erythrocytes (E) sensitized with mIgG1 as target cells, Fc gamma RII was studied selectively. Cells which had been cultured for 40 h exhibit a significantly decreased Fc gamma RII expression, and Fc gamma RII-mediated ADCC activity as compared with freshly isolated monocytes. Co-culture with rIFN-gamma (40 h) reversed this decrease. Short-term rIFN-gamma-cultured cells, and fresh cells express similar numbers of Fc gamma RII, and exhibit comparable Fc gamma RII-mediated ADCC activity. Phagocytic activity was not affected. Prolonged culture of monocytes for 9 days, co-cultured with rIFN-gamma either from day 0 or from day 7, did not affect expression or functional activity of Fc gamma RII. Furthermore, the effects were observed in both HR and LR individuals. Our results show that rIFN-gamma has strong effects on Fc gamma RII-mediated responses specifically during the early stages of monocyte maturation, most likely by affecting receptor expression levels.

In vitro studies on the influence of doxorubicin in combination with recombinant interferon-gamma on human monocytes.

The maturation and differentiation process of human monocytes and human monocyte-derived macrophage cytotoxicity mediated by receptors for the Fc moiety of immunoglobulin G (Fc gamma Rs) were studied in vitro using the chemotherapeutic drug doxorubicin in combination with the biological response modifier (BRM) recombinant interferon-gamma (rIFN-gamma). Human monocytes were cultured for 9 days and treated with doxorubicin before, after, or on day 7 of the culture. rIFN-gamma was added continuously on day 0 or on day 7 of the culture, either alone or in combination with doxorubicin. In the presence of doxorubicin, all measured intracellular enzyme activities were at the same level as the controls and the rIFN-gamma treated cells. However, when monocytes were co-cultured for 9 days with rIFN-gamma alone or in combination with doxorubicin, enzyme levels decreased to between 45% and 61% of the controls. In control cultures ADCC activities against maximally sensitized hRBC mediated by Fc gamma RI and Fc gamma RII were 41.7 +/- 8.8% and 42.7 +/- 11.6%, respectively. When monocytes were exposed to rIFN-gamma continuously or 40 h before harvesting, Fc gamma RI ADCC activity increased to 78.9 +/- 9.8% and 68.1 +/- 8.1%, respectively, and Fc gamma RII ADCC activity to 56.3 +/- 8.4% and 55.4 +/- 7.3%, respectively. The addition of doxorubicin to monocyte cultures in the presence or absence of rIFN-gamma did not influence the lysis of the two types of sensitized hRBC. These observations indicate that doxorubicin does not negatively influence the activation state of monocytes/macrophages, induced by rIFN-gamma.

Effects of doxorubicin on maturation of human monocytes in adherent and non-adherent cultures.

Purified human monocytes were cultured for 2 h, 88 h, and 10 days in plastic tubes (adherent) and for 10 days in Teflon foil bags (non-adherent). Monocytes were incubated with doxorubicin by two short-term exposures (750 or 1500 ng/ml) for 1 h or by continuous exposure (75 ng/ml). Maturation was monitored by measuring the intracellular activity of three metabolic enzymes and two acid hydrolases. Expression of receptors for the Fc moiety of immunoglobulin G (FcRI, FcRII, FcRIII), CD14, and HLA-DR was assayed by indirect immunofluorescence with monoclonal antibodies. In the presence of doxorubicin, the adherent capacity, the yield, and the enzyme activities reflecting growth and intermediary metabolism were similar to the control groups. However, doxorubicin reduced the expression of FcRI (32-45%), FcRII (10-26%), CD14 (20-37%), and HLA-DR (25-34%) on the monocyte-derived macrophages. Expression of FcRIII was not detectable after 10 days of culture.