ANTIBODY-FACILITATED MACROPHAGE KILLING OF TRYPANOSOMA-MUSCULI IS AN EXTRACELLULAR PROCESS AS STUDIED IN SEVERAL VARIATIONS OF AN IN-VITRO ANALYTICAL SYSTEM

Antibody-facilitated macrophage (MP) destruction of Trypanosoma muscul i involves ingestion and intracellular degradation of the parasites. I t is likely, however, as we show here, that death of the trypanosomes is extracellular and it is the corpses that are ingested by MPs. We ha ve utilized both peritoneal MPs and a cloned line (WLG 5) of mouse MPs to analyze the killing of T. musculi. Both types of MP were more effe ctive when activated by interferon-gamma (IFN-gamma) rather than lipop olysaccharide (LPS). When activated by both, LPS diminished the killin g activity stimulated by IFN-gamma, perhaps by changing the spectrum o f lysins/toxins released by the MPs. Nitric oxide (NO) was found to be toxic for T. musculi and to be responsible, in part, for MP killing o f the parasites. Although antibody and complement in concert caused ly sis of T musculi, complement was not required for MP killing of the pa rasites. In the course of this investigation, we developed an in vitro system, involving line 5 MPs and plasma from infected mice containing resident parasites, that should prove satisfactory for detailed analy ses of the mechanisms of the antibody-dependent, cell-mediated cure of T. musculi infection.