Lymphocyte-mediated cytotoxicity on human tumor cells in vitro.

Tumor cells of 30 patients suffering from different kinds of malignant tumors were established in culture. Various numbers of autologous and allogeneic PHA-stimulated as well as not stimulated lymphocytes were added to the cultures. 48 hours later, as evaluated by morphological observation, the lymphocytes caused a more or less cytotoxic effect in 80% of the cases, which is believed to be specific. This effect was distinctly inhibited in presence of the patient's own plasma in 71% in the sense of immunological enhancement. Cross reactivity between two patients having the same type of tumor was observed. The cytotoxic effect shows a certain correlation to the PHA transformation ability and increases with increasing numbers of lymphoid cells applied. It is supposed that in this manner the strength of an existing cell-mediated immunity against the tumor in every individual patient possibly can be assessed and, besides, an inhibiting humoral factor can be found out. Perhaps this can be valuable as an indicator for chemotherapy and immunotherapy of cancer.