To elucidate the local tissue cytokine response of dogs infected withLeishmania chagasi,cytokine mRNA levels were measured in bone marrow aspirates from 27 naturally infecteddogs from Brazil and were compared with those from 5 uninfected control animals. Interferon-gmRNA accumulation was enhanced in infected dogs and was positively correlated withhumoral (IgG1) but not with lymphoproliferative responses toLeishmaniaantigen in infecteddogs. Increased accumulation of mRNA for interleukin (IL)?4, IL-10, and IL-18 was notobserved in infected dogs, and mRNA for these cytokines did not correlate with antibody orproliferative responses. However, infected dogs with detectable IL-4 mRNA had significantlymore severe symptoms. IL-13 mRNA was not detectable in either control or infected dogs.These data suggest that clinical symptoms are not due to a deficiency in interferon-gpro-duction. However, in contrast to its role in human visceral leishmaniasis, IL-10 may not playa key immunosuppressive role in dogs.
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