Cellular microcytotoxicity in human tumor systems: analysis of results.

Using the tritiated-proline microcytotoxicity assay with cultured target cells, we tested a large series of melanoma, breast cancer, and bladder cancer patients for the presence of cell-mediated immunity. Specific, disease-related activity was infrequently observed, since the patients' lymphocytes exhibited selective activity against both disease-related and non-disease-related target cells. Most normal controls also demonstrated selective activity against these target cells. Neither the length of time the target cells had been cultured in vitro nor technical aspects of the assay, including the lymphocyte preparation methods, seemed to account for our results. We concluded that the experimental design of these tests may be the critical factor responsible for many of the disparate results being observed in different laboratories.