The role of interleukin 10 (IL-10) and gamma interferon (IFN-␥) on the development of pathology in human Chagas' disease was investigated. Two categories of patients, low and high producers of IFN-␥, were identified based on the levels of secretion of this cytokine in the supernatant of peripheral blood mononuclear cell (PBMC) cultures. Eighty-three percent of the patients presenting with cardiac disease (CARD) of different degrees and 59% of the patients with the indeterminate form of disease (IND) were identified as high IFN-␥ producers. PBMC from IND patients classified as low IFN-␥ producers secreted significantly higher amounts of IL-10 than did those from other groups. Flow cytometry analysis demonstrated that in PBMC from the IND group, the majority of the IL-10-producing cells were monocytes (CD14 High؉ cells), whereas in the CARD group, the major sources of IFN-␥ were T lymphocytes (CD3 ؉ CD4 ؉ cells). These results suggest an association between the production of IFN-␥ by CD3؉ CD4 ؉ cells and morbidity in Chagas' disease, whereas the production of IL-10 by macrophages/monocytes leads to regulation of the immune response in IND patients. We hypothesize that an exacerbated production of IFN-␥ against Trypanosoma cruzi antigens favors the development of a strong Th1 response in CARD patients, which leads to progression of heart disease.

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This review discusses the large-scale laboratory maintenance of Schistosoma mansoni. Emphasized are features which increase efficiency in such facilities, and problems most frequently encountered. Profiles are given of the long-term, high-level production of 3 strains of S. mansoni. Two of the strains, NMRI and PR-1, were of Puerto Rican origin and the other, LE, was from Brazil. Three to 8 million cercariae of each strain were usually obtained per week. The most obvious differences between the 3 strains were cercarial output per snail and snail mortality rates. Maintenance problems encountered were usually related to water quality, temperature, genetics of the parasite or snail host, predators or contaminants, feeding, or crowding of snails. Examination of the production data from these 3 life cycles led to identification of features that could be of benefit for increasing the productivity and efficiency of other S. mansoni life cycles used in research activities.