Two distinctive patterns of monocyte immunoregulatory and effector functions in heavy human infections with Schistosoma mansoni

We evaluated the relationship between immunoregulatory and effector functions of monocytes in subjects with heavy S. mansoni infection (> 400 eggs/g of stool). Two main patterns were found. In seven individuals (mean 601 eggs/g), the depletion of adherent cells from peripheral blood mononuclear cells (PBMC) increased blastogenic responses to soluble worm antigenic preparation (SWAP) from a stimulation index (SI) of 3.2 ± 1.0 to 11.0 ± 3.0 (p <0.01). The presence of indomethacin (1.0 μg/ml) in cultures of PBMC from these subjects increased the SWAP response to 7.1 ± 2.0 (p <.05). In contrast, neither adherent cell depletion nor indomethacin affected blastogenesis induced by nonschistosome antigens or nonspecific mitogens. In this group of infected individuals, monocyte killing of schistosomula and adherence to plastic were increased 122% (p <0.01) and 50% (p <0.01) over the respective values obtained in uninfected, age-matched controls. A second pattern was found in 10 individuals with a significantly higher intensity of infection (1339 eggs/g of stool (p <0.02)). PBMC from these subjects failed to respond significantly to SWAP (SI = 2.0 ± 0.5), whereas the levels of responses to other antigens and mitogens were maintained at rates comparable to controls. Adherent cell depletion did not significantly affect the blastogenic response (1.8 ± 0.2), nor did the presence of indomethacin in cultures (2.0 ± 0.5). Moreover, monocyte-mediated schistosomula killing was depressed in these individuals (50% of controls, p <0.05) as was adherence to plastic (77% of controls, p <0.05).