Characterization of in vitro proliferative responses of human lymphocytes to leishmanial antigens.

Leishmaniasis is an intracellular protozoal infection for which host defense is believed to depend on cellular immune mechanisms. The in vitro proliferative responses of lymphocytes from patients with leishmaniasis and from control subjects to leishmanial antigens were examined. Only lymphocytes from patients responded to 1 microgram of leishmanial antigen/ml, whereas both patient and control lymphocytes responded to 10 micrograms/ml. The nonspecific responses were most likely not due to a mitogenic component in the antigen preparation because cord blood lymphocytes failed to respond at all concentrations of antigen tested. Both specific and nonspecific responses to leishmanial antigens were elicited in purified populations of thymus-derived (T) cells. This lymphocyte proliferation assay can be applied to the assessment of antigen-specific responsiveness of T cells from patients who represent the spectrum of host defense against leishmaniasis.