Effect of commercial immunoglobulin G preparation on human monocyte Fc-receptor dependent binding of antibody coated platelets

This study examined the in vitro effect of a commercial immunoglobulin preparation on human monocytes and the Fc-receptor dependent binding of antibody coated platelets. Monocytes were exposed to Sandoglobulin® in vitro and subsequently examined for membrane surface bound IgG. Dramatic increments of surface IgG were found which were maximal with 18 h exposure and somewhat higher at 4°C than 37°C. Ultracentrifugations of Sandoglobulin® immediately prior to monocyte exposure reduced the monocyte membrane IgG by 75%. The 18 h exposure at 37°C produced dramatic impairment of monocyte Fc-receptor binding of IgG coated platelets (P < 0.001) while exposure for 18 h at 4°C produced a modest impairment of Fc-receptor function. These studies indicate that Sandoglobulin® contains IgG aggregates which are able to firmly bind to the monocyte surface in a time and temperature dependent fashion. The dramatic impairment of Fc-receptor function at 37°C and not at 4°C suggests that Fc-receptor modulation, as well as competitive inhibition/steric hindrance, contribute to impairment of monocyte Fc-receptor function.