Monocyte procoagulant activity induced by concanavalin A is decreased in a population of chronic chagasic patients.

: 1. The ability of peripheral blood mononuclear cells (PBMC) from Chagas' disease patients to induce monocyte procoagulant activity (PCA) in response to concanavalin A (Con A) and to a Con A induced lymphokine was studied. 2. In spite of the variability of PCA levels among both chagasic patients and normal controls, statistical analysis of the data permitted us to draw the following general conclusions. 3. The Con A-induced monocyte PCA measured in 17 assays of 15 chagasic patients was significantly lower than the PCA response of 18 normal controls or of 11 patients with non-chagasic myocardiopathies. 4. The response of PBMC from chagasic patients to lymphokine was also lower than that observed for normal controls. 5. These results suggest that monocytes from chagasic patients are deficient for the generation of PCA which is an in vitro correlate of the delayed-type hypersensitivity reaction.