INTERFERON-GAMMA-ACTIVATED IMMATURE MACROPHAGES EXHIBIT A HIGH TRYPANOSOMA-CRUZI INFECTION-RATE ASSOCIATED WITH A LOW PRODUCTION OF BOTH NITRIC-OXIDE AND TUMOR-NECROSIS-FACTOR-ALPHA

Murine peritoneal macrophages (MPM) can be subdivided into two subpopu lations of mature and immature macrophages. In contrast to mature macr ophages, immature ones were highly susceptible to Trypanosoma cruzi in fection. This high susceptibility was associated with a low production of alpha(2)-macro,olobulin. Interferon-gamma (IFN-gamma)-activated im mature macrophages also exhibited a higher infection rate than did IFN -gamma-activated mature ones. This higher rate of infection was associ ated with a low production of both nitric oxide (N=O) and tumor necros is factor-a (TFN-alpha). In contrast, mature MPM showed a lower rate o f infection and produced higher levels of N=O and TFN-alpha. Taken tog ether, these results show a clear-cut difference in the course of T. c ruzi infection in relation to the macrophage maturation state.