Lymphokine activation of J774G8 cells and mouse peritoneal macrophages challenged with Toxoplasma gondii.

In vitro activation of macrophage cell line J774G8 and mouse peritoneal macrophages resulted in oxygen-dependent and oxygen-independent killing of intracellular Toxoplasma gondii. Activation was characterized by oxygen-dependent killing detectable by enhanced lysosome fusion and digestion of T. gondii. The toxoplasmacidal activity of activated J774G8 cells and peritoneal macrophages was prevented by adding the oxygen intermediate scavengers catalase or superoxide dismutase during culture. Activated J774G8 cells and peritoneal macrophages also inhibited replication of those Toxoplasma organisms which survived the initial microbicidal activity. The inhibition of Toxoplasma replication was not significantly affected by exogenous catalase or superoxide dismutase. Peritoneal macrophages from Toxoplasma-immune mice showed similar microbicidal and inhibitory responses, supporting the model that activation leads to destruction of intracellular parasites by two different mechanisms.