Peripheral blood lymphoid cells (PBL) from cancer patients and normal donors were tested against three melanoma cell lines grown in either 10% fetal calf serum (FCS) or 2.5-5% human AB serum in order to determine if the heterologous membrane (HM) antigen or other FCS antigens acquired from the bovine serum supplement could influence lymphoid cell-mediated cytotoxicity in vitro. FCS-grown melanoma cells were more susceptible than the AB serum-grown subline to lymphocyte cytotoxic effects. Arming effects by autologous sera on normal donor lymphocytes and to a lesser extent on lymphocytes of cancer patients were more pronounced on the FCS-grown M12 melanoma cells. This effect was abrogated when the cells were grown in human AB serum for at least 8 weeks. The non-HM tumor-associated antigen remained at the same original low level. Blocking effects were more evident on the AB-grown M14 melanoma line. These data suggest that the FCS antigens on the cell surface may have been responsible for the augmented PBL cytotoxicity. The anti-FCS antibody present in normal and cancer patients' blood induced an antibody-dependent cellular cytotoxicity (ADCC). Elimination of arming activity against HM or other FCS antigens from AB-grown cells may have made the serum blocking factors more apparent. However, cytotoxicity against tumor cells by PBL from normal donors was still apparent even on the human serum-grown cells, suggesting that a different antigen-antibody system was also responsible for this "non-specific" activity.
Human tumor and febroblast tissue culture cells were compared to determine the suitability of fibroblasts as control cells in experiments on human tumor serology and cellular immunology. Fibroblasts expressed the same HL-A antigen profile as did melanoma cells. Furthermore, the quantitative expression of the determinants was similar on both cell types. In four of five pairs tested, the fibroblasts displayed similar sensitivity to effector cells generated by mixed lymphocyte culture as did the tumor cells from the same donor, but there were some differences in the effects of specific alloimmune effector cells at high and low effector-to-target ratios on the two types of target cells. Results indicated that fibroblasts are legitimate control target cells for studies in human tumor immunology, if screening assays are done to verify their antigenicity and sensitivity to cell-mediated cytolysis.
The therapeutic efficacy of intralesional BCG (Bacillus Calmette‐Guerin; one immunizing dose every 2 weeks for a minimum of five treatments) was studied in 19 melanoma patients. Of 15 patients evaluable for response, five experienced significant objective improvement (two complete and three partial remissions). Objective improvement was limited to those patients with dermal metastatic disease. In vitro cytotoxicity in the presence of patient's serum bore, on average, a relationship to the clinical disease. In certain individual cases, serum blocking and/or lymphocyte stimulation may have had prognostic significance.
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