Killing of schistosomula of Schistosoma mansoni by macrophages: induction by T-cell clone-derived lymphokines and interferon-gamma.

The induction of schistosomulicidal activity of peritoneal macrophages by concanavalin A-stimulated supernatants from long-term T-cell clones and by interferon-gamma (IFN-gamma) was investigated in detail. Optimal conditions of in vitro macrophage activation by T-cell clone supernatants were established. Macrophages from 13-week S. mansoni-infected mice responded to lymphokine activation as well as resident macrophages from uninfected mice. IFN-gamma was shown to play an essential role in induction of schistosomulicidal macrophage activity: recombinant IFN-gamma at high concentration could induce schistosomula killing, and an anti-IFN-gamma antiserum inhibited the induction of schistosomulicidal activity by T-cell clone supernatants. Our data also indicate that macrophage activation could be obtained by IFN-gamma in synergy with other lymphokines in the supernatant of long-term T-cell clones. Macrophages from mice injected with T-cell clone supernatants were primed in vivo and triggered to kill schistosomula in vitro in the presence of lipopolysaccharide (LPS). The data demonstrate that lymphokines produced by T-cell clones and, in particular, IFN-gamma can participate in the activation of schistosomulicidal macrophages.