REPORTS In Vitro Induction of Tumor Necrosis Factor a, Tumor Cytolysis, and Blast Transformation by Spiroplasma

were potent inducers of tumor necrosis factor a (TNFa) secretion and of blast transformation. Specific anti-recombi-nant murine TNFa antibodies mark-edly inhibited macrophage-mediated tumor cytolysis of A9 fibrosarcoma tar-get cells following activation by MQ-1 membranes. Thus, TNFa plays a major role in mediation of tumor cytolysis in-duced by MQ-1 membranes, which is similar to its role in lipopolysaccharide (LPS)-induced tumor cytolysis. Two findings, however, suggested that the mechanism of macrophage activation by MQ-1 membranes differs from tha