Effects of methylprednisolone on the Fc-receptor function of human reticuloendothelial system in vivo

To determine whether the Fc-receptor function of reticuloendothelial system (RES) is modified by corticosteroid administration, we studied the spleen to liver uptake ratios of autologous, 99Tc-labelled heat-damaged or IgG-coated erythrocytes, injected intravenously into 10 normal volunteers, 4 h after receiving a single dose of 32 mg of methylprednisolone by mouth. In standard conditions, quantitative scans indicated that the spleen to liver uptake ratios, calculated per unit area 40 min after the injection of labelled erythrocytes, were 13.4 +/- 0.6 and 31.2 +/- 1.5 (mean values +/- -SEM), for the heat-damaged (n = 7) and IgG-coated red cells (n = 5) respectively. Four hours after corticosteroid administration, the spleen to liver uptake ratios were significantly reduced in five of ten volunteers. Abnormal ratios correlated with the Fc-receptor function of monocytes measured in vitro using IgG-coated erythrocytes. Indeed, 2-6 h after methylprednisolone was given, the Fc-receptor binding activity of monocytes isolated from the same five subjects was reduced by at least 50%, spontaneously returning to a rather normal value 4-6 h later. The C3-receptor binding activity of these monocytes remained normal, after otherwise identical experimental conditions. These results show a transient, specific impairment of the Fc-receptor function of RES after methylprednisolone administration, and may therefore explain, in part, the infectious complications occurring in some patients treated by corticosteroids.