Visceral leishmaniasis: a disease associated with inability of lymphocytes to activate macrophages to kill leishmania.

1. The production of lymphokines capable of activating macrophages to kill leishmania was evaluated in seven visceral leishmaniasis patients. 2. Macrophages from healthy donors cultivated in vitro with supernatants from lymphocyte cultures of visceral leishmaniasis patients were infected with L. d. chagasi or L. m. amazonensis. After infection the number of amastigotes per 100 cells was counted. 3. The supernatant from visceral leishmaniasis lymphocytes did not significantly reduce the number of intracellular amastigotes of L. donovani chagasi (89 +/- 27%) in relation to controls (culture containing medium alone). In contrast, supernatants of mucocutaneous lymphocyte cultures decreased the percentage of infection to 26 +/- 11%. The supernatant of antigen-stimulated lymphocyte cultures from visceral leishmaniasis patients also did not inhibit L. mexicana amazonensis growth. The supernatant of visceral leishmaniasis lymphocytes stimulated with PHA reduced the number of intracellular amastigotes to 62 +/- 23% in relation to controls. 4. The inability of lymphocytes from visceral leishmaniasis patients to proliferate when stimulated with leishmania antigens and to activate macrophages to kill leishmania may represent a fundamental defect and lead to the acquisition of the disease.