Proliferation pattern of hamster melanoma cells cultured in diffusion chambers in pre-immunized hosts.

Fortner M Mel 1 melanoma cells from the Golden Hamster were capable of exponential proliferation during intraperitoneal diffusion chamber culture in xenogenic host animals (Balb/c mice, BD IX and Marshall rats). When the host animals had been preimmunized with these melanoma cells, rapid cell lysis was observed in the chambers within 4 hrs after implantation. The cell numbers were reduced to about 1 - 10% of the inoculum. At this level the cell numbers persisted for several days, as opposed to control cultures in untreated hosts, where the cells proliferated rapidly. After 6 - 10 days the cell numbers in chambers from immunized hosts slowly increased in spite of a high level of cytotoxicity in ther serum of the animals. The same pattern was seen after previous immunization with hamster lymphocytes, indicating that the antibodies were directed against a common antigen for melanoma cells and lymphocytes in hamsters. The diffusion chamber method appears to be a useful system for the study of a pure humoral immune reaction against tumour cells, and especially for investigation of the phenomenon that some tumour cells are able to escape a strong humoral cytotoxic effect from host animals.