Antibody-dependent cell-mediated cytotoxicity against melanoma cells induced by plasmapheresis

Patients with disseminated melanoma were treated by repeated plasmapheresis using a continuous-flow blood-cell separator, as part of a study to investigate methods of removing factors from tissue fluids which block cell-mediated immunity. Using 51Cr release cytotoxic assays, it was found that plasmapheresis resulted in removal of serum blocking activity. Post-plasmapheresis sera taken from several patients also increased cell-mediated cytotoxicity by induction of antibody-dependent cell-mediated killing. This effect may have resulted from removal or alteration of circulating immune complexes in the serum. It is not known whether cytotoxic activity induced in this way improves the patient's immune response against their tumours. However, the procedure is well tolerated and these preliminary in-vitro results indicate that this form of therapy could act as an adjunct to other forms of treatment of advanced melanoma.