Inhibition of PMA-elicited oxidative burst of human monocytes fed with trophozoites, delipidized trophozoites, or hemozoin.

Suspended monocytes were incubated after addition of nonparasitized RBCs (■), trophozoites (▥), isolated hemozoin (▪), or delipidized trophozoites (▨). Cells and hemozoin were opsonized as indicated and added at time zero to the monocyte suspension at 50 RBC/RBC equivalents (hemozoin) per monocyte. In all cases the same amount of heme was fed to the monocytes. The monocytes were kept in the humidified CO₂/air incubator at 37°C, and PMA-elicited oxidative burst was quantified by measuring luminescence in a luminol-dependent assay at the indicated times. Luminescence values are expressed as counts per second per 411 monocytes. For details, see “Materials and methods.” One experiment representative of 4 with similar results is shown.