Interleukin-2-stimulated natural killer activity against malignant and benign endometrium

Natural cell-mediated immunity against autologous tumor cells, autologous endometrial epithelium, and allogeneic epidermoid carcinoma cell line HeLa was tested in 8 patients with endometrial carcinoma and one patient with endometrial stromal sarcoma. The average cytotoxicity of unstimulated peripheral blood lymphocytes against autologous tumor and HeLa cells was weak but significant. Pretreatment of effector cells for 3-5 days with 300 U/ml recombinant interleukin-2 (rIL-2) resulted in increased cytotoxicity against malignant target cells in 7 out of 9 cases. The 2 patients' effector cells which were refractory to rIL-2 could be stimulated to appreciable lytic activity against the malignant target cells with a recently described cytokine which induces morphological differentiation of natural killer cells. Benign endometrial cells were weakly sensitive to rIL-2-activated lysis in 2 cases. The precursors of the rIL-2-activated killer cells were mostly CD16-positive and CD3-negative, and co-sedimented with endogenous natural killer cells in discontinuous density gradient centrifugations. These results indicate the rIL-2-activated killer cells have a capacity to distinguish between normal and malignant endometrial cells, and that the precursors of the lytic cells in this system belong to the same subpopulation of lymphocytes as endogenous natural killer cells. In addition, rIL-2 alone may not in all cases be sufficient for optimal generation of cytotoxicity against malignant cells.