Effect of human monocyte killing of tumour cells of antibody raised against an extracellular monocyte cytotoxin.

Human monocytes can kill or inhibit the growth of certain tumour cell lines. Amongst the possible mediators is a cytotoxin synthesized in readily detectable amounts by endotoxin-stimulated monocytes. A neutralizing antiserum to the cytotoxin has been used to assess the cytotoxin's contribution to monocyte killing of tumour cells. The antiserum was tested for possible inhibition of monocyte killing of three tumour cell lines--L929, K562 and A549. Inhibition was complete with L929, partial with K562 and insignificant with A549. Thus the contribution of the cytotoxin to monocyte killing of tumour cells depends upon the tumour line under test. Antibody against endotoxin-induced cytotoxin also neutralized cytotoxin induced in monocytes by other agents including BCG, Corynebacterium parvum, pokeweed mitogen and zymosan. Cytotoxin could be quantitatively removed from monocyte supernatants by Sepharose-bound, anticytotoxin antibody. Recovery of the cytotoxin from the immunoadsorbent was difficult because of its lability in the solutions commonly used for desorption. The best recovery has been achieved with 2 M urea, 2 M MgCl2 giving a 25% yield and a forty-fold increase in purity in a single step.