Gamma interferon production by lymphocytes from children infected with L. chagasi.

The present study was performed to evaluate the ability of lymphocytes from 18 children living in an endemic area of visceral leishmaniasis (VL) to produce gamma-interferon. These children had no previous history of VL and were considered to be infected with Leishmania chagasi based on leishmanial seroconversion. The gamma IFN levels were determined by radioimmunoassay on supernatants of lymphocyte cultures (3 x 10(6)/ml) stimulated with PHA (final dilution 1:10) and Leishmania chagasi antigen (10 micrograms/ml). The gamma-IFN production by lymphocytes from seroconverting children stimulated with PHA (178 +/- 151 U/ml) and Leishmania chagasi (47 +/- 77 U/ml) was significantly higher than that observed in visceral leishmaniasis. For clinical follow-up, these 18 seroconverting children were divided into three groups: asymptomatic infection (N = 4); self-healing subclinical illness (N = 9), and subclinical infection progressing to VL (N = 5). Gamma IFN levels in children with either asymptomatic or subclinical infection (65 +/- 85 U/ml) were significantly higher (P less than 0.003) than those observed in children progressing to VL (9 +/- 6 U/ml). The data demonstrate that there is an association between gamma IFN levels and the clinical course of Leishmania infection.