The concept of immunotherapy of human sarcomas: the need for an in vitro monitoring assay.

Patients with sarcomas circulate a population of lymphocytes that exert cytotoxicity to cultured sarcoma cells; these lymphocytes behave as if pre­ sensitization to sarcoma-distinctive antigen(s) occurred already in vivo. This cytotoxic effect can be abrogated by sarcoma-specific blocking serum factors. Another “noncommitted” population of lymphocytes may gain d e novo immune reactivity to allogeneic cells in vitro but this reaction requires several days of cocultivation. This cytotoxic effect cannot be abrogated by sarcoma-specific serum blocking factors. A well standardized and well controlled in vitro assay for the monitoring of tumor-specific immune reactions of patients would be of great value in the se­ lection of those therapeutic modalities that favor antitumor immune reactions.