Studies on the antibodies and the role of complement in autologous humoral cytotoxicity to human neoplasms

Using neoplastic cell cultures and autologous plasma and serums, investigations were made into some of the characteristics of the cytotoxic antibody populations and the part played by complement in this cytotoxic activity. It was discovered upon heat inactivation of plasma samples and exposure to the autologous cells that the level of toxicity after heat-inactivation was decreased in 5 of 10 cases, increased in 3 of 10 cases, and remained the same in 2 of 10. Quantitation by both the cell inhibition and colony inhibition assays were performed with the plasma samples being titrated to an end point. Survival of cells was always greater as measured by cell quantitation; an average of 22 percent. Upon titration of an individual autologous plasma, inhibition by the colony assay was no longer present at a 1:32 dilution and by cell quantitation at a 1:512 dilution. When efforts were made to reconstitute activity lost by heat inactivation, three samples were fully reconstituted, two were partially and one was not, as measured by cell quantitation. Using the same samples with quantitation by the colony assay, two were fully reconstitutable and two were not. When samples were stored at -80°C and retested at intervals, it was found that the cytotoxic activity declined rapidly with cytotoxic activity, as measured by the colony assay, no longer present after 30 days, but still with residual cytotoxic activity as measured by cell quantitation. It was also noted that cytotoxic activity, not reconstitutable by exogenous complement, after heat inactivation was also extremely labile at low temperatures, whereas the complement dependent activity was much less affected. By titration of complement with heat inactivated and carragheenan inactivated serum, a ratio of 1CC50 = 12.5 CH50 was computed.