Production of Interleukin-6 by Human and Murine Mononuclear Leukocytes Stimulated with Plasmodium Antigens Is Enhanced by Pentoxifylline, and Tumor Necrosis Factor Secretion Is Reduced

When pentoxifylline was present during stimulation of human mononuclear leukocytes with Plasmodium falciparum exogenous antigens, an increase in interleukin-6 production was observed simultaneously with a reduction of tumor necrosis factor secretion. Similar results were obtained in murine macrophages stimulated with P. vinckei antigens. This indicates the independence of interleukin-6 and tumor necrosis factor secretion in response to malaria antigens. The production of cytokines such as tumor necrosis factor (TNF) and interleukin-6 (IL-6) has been found to play a role in protection against malaria parasites and also in the pathol-ogy of human malarial disease (5, 8-13, 16). The production of high concentrations of TNF by human and murine mac-rophages as a response to malaria antigens has also been reported previously (2, 3, 13, 20, 23-25). The induction of IL-6 by TNF (9, 19) and the detection of high levels of IL-6 in cases of complicated Plasmodium falciparum malaria (7, 11) led us to investigate the production of IL-6 by macro