title: Human monocyte-derived macrophages are lysed by schistosomula of Schistosoma mansoni and fail to kill the parasite after activation with interferon gamma.
abstract: In this study was examined the interaction between schistosomula of Schistosoma mansoni and human monocyte-derived macrophages activated with interferon gamma (IFN-gamma). Peripheral blood monocytes were matured for 6 days and activated by further culture with IFN-gamma (600 U/ml). These IFN-gamma-treated monocyte-derived macrophages are cytotoxic for the tumor cell line K562, which is not killed by nonactivated monocyte-derived macrophages. Activated monocyte-derived macrophages were incubated with schistosomula at ratios of 10(3):1 and 10(4):1 in the presence of serum pooled from patients with schistosomiasis. This antiserum promoted an increased adherence of cells to the parasite. However, the activated monocyte-derived macrophages failed to kill the schistosomula under all conditions tested. On the contrary, the monocyte-derived macrophages were killed by schistosomula in a time-dependent and antibody-dependent manner, which was most evident at a lower effector/target ratio, 200:1. Electron microscopy showed that monocyte-derived macrophages were lysed on the surface of schistosomula. Further, both monocyte-derived macrophages and contaminating blood platelets fused with the parasite surface membrane, so that the cell plasma membrane and the outer tegumental membrane formed a hybrid membrane. The results indicate that matured human monocyte-derived macrophages activated by IFN-gamma are unable to kill schistosomula. Instead, the effector cells fuse with the parasites and are lysed by them.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006801:Humans; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000494:pharmacology*; D008262:Macrophage Activation; D008264:Macrophages / Q000187:drug effects / Q000469:parasitology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D012550:Schistosoma mansoni / Q000472:pathogenicity*
chemical_list: D007371:Interferon-gamma