Fcγ receptor activation by IgG enhances IL-1β but not IL-6 secretion in the absence of IE ingestion. MDM were grown in Teflon jars for five days, primed for 48 hr with 100 ng/ml IFN-γ and then seeded in triplicate onto wells of 96-well tissue culture plates coated with human IgG (●) or left uncoated (○). After MDM had adhered, they were incubated with unopsonized CS2 IE at an IE:MDM ratio of 20:1. After 24 hr culture medium was collected and analysed for secretion of (A) IL-1β (B) TNF and (C) IL-6. Data represent mean ± SEM of six separate experiments using MDM prepared from independent donor monocytes. Differences at each time point were tested for significance using Wilcoxon matched pairs test; * p<0.05. (D) In selected experiments MDM were also seeded in triplicate onto IgG-coated (grey bars) or uncoated (white bars) wells of a separate plate, and phagocytosis of human erythrocytes (E), unopsonized CS2 IE, CS2 IE opsonized with pooled immune patient serum (IE-PPS) and human erythrocytes opsonized with rabbit anti-human erythrocyte antibody (E-IgG) was measured. Data represent mean ±SEM of triplicate measurements from a single representative experiment.