Lymphocyte mediated reactivity against malignant melanoma detected by a microcytotoxicity assay employing technetium-99m labeled target cells

Abstract

The 99mTc microcytotoxicity assay has been employed to study the reactivity of peripheral blood lymphocytes from 40 melanoma patients and 58 normal donors against target cells cultured from 16 melanomas, 4 bronchogenic carcinomas, a colon carcinoma and an osteogenic sarcoma. Lymphocytes from 31 of 40 (78%) melanoma patients were cytotoxic to at least one melanoma cell line in 38 of 50 experiments (76%). This level of reactivity was significantly different (p ⩽ 0.001) from that of normal donors' lymphocytes (17/58 cytotoxic experiments, 29%). Absence of histologic type-specific reactivity was evidenced by cytotoxicity of lymphocytes from 23 of 36 (64%) melanoma patients against at least 1 non-melanoma cell line (28/43 experiments, 65%). Normal donors' (17/50, 34%) lymphocytes gave significantly (p ⩽ 0.02) fewer cytotoxic reactions against nonmelanoma cell lines. The predominant response of melanoma patients' lymphocytes was non-selective cytotoxicity as reflected by reactivity against melanoma and nonmelanoma tumor target cells simultaneously in the majority of experiments (24/43, 56%). Nonselective cytotoxicity appeared to increase in frequency with extent of disease. Significantly (p ⩽ 0.01) more patients with Stage III melanoma (13/15, 87%) than those with Stage I melanoma (4/11, 36%) had lymphocytes cytotoxic to both melanoma and nonmelanoma target cells. Nonselective cytotoxicity of lymphocytes from patients with Stage II melanoma (7/11, 64%) was intermediate in occurrence. An increased frequency of tumor-specific cytotoxic reactions was observed in those experiments which utilized two or more melanoma or nonmelanoma target cell lines. This suggests that it might have been possible to distinguish tumorspecific from tumor-associated reactivity if a sufficiently large number of target cell lines had been employed.