INTERLEUKIN-6 (IL-6) PRODUCTION IN MICE INFECTED WITH TRYPANOSOMA-CRUZI - EFFECT OF ITS PARADOXICAL INCREASE BY ANTI-IL-6 MONOCLONAL-ANTIBODY TREATMENT ON INFECTION AND ACUTE-PHASE AND HUMORAL IMMUNE-RESPONSES

Trypanosoma cruzi infection of mice triggered endogenous production of interleukin-6 (IL-6) during the ascending phase of parasitemia. Injec tions of anti-IL-6 monoclonal antibody in infected mice at the time of the serum IL-6 peak paradoxically increased IL-6 levels to 60- to 80- fold those in infected mice receiving unrelated immunoglobulins. This early and transient increase in circulating IL-6 levels modified neith er the immunoglobulin nor T. cruzi-specific antibody levels of immunog lobulin G1 (IgG1), IgG2a, IgG2b, IgG3, IgM, IgA, and IgE isotypes or t he final outcome of infection nor the blood or tissular parasite level s. However, it tended to delay mortality of mite and to increase the l evels of the acute-phase protein serum amyloid P component.