Abstract
The mechanisms underlying the failure to contain the growth of Leishmania parasites in human visceral leishmaniasis (VL) are not understood. L donovani amastigotes were quantified in cultured splenic aspirate cells to assess the function of IL-10 in lesional tissue ex vivo. In 67 patients with active VL, IL-10 neutralization promoted parasite killing in 73% and complete clearance in 30%, while 18% had more parasites and 9% did not change. The splenic cells secreted increased levels of both tumor necrosis factor α (TNFα) and interferon γ (IFNγ) under IL-10-neutralizing conditions. These findings provide direct support for targeting IL-10 as an approach to therapy in human VL.