Action of natural killer cells and macrophages in cancer.

According to the results obtained in several types of experiments the immunological anti-tumor effects that reflect the clinical situation involve T lymphocytes. The products of natural effector cells can contribute to anti-tumor immunity as part of the cytokine network. In addition, some cytokines can act on the tumor cells by influencing directly their proliferative capacity and/or through modification of their phenotype. In the tumor tissue the interaction between malignant cells and host cells on the one hand, and between the various types of host cells on the other hand, is complex. The participating mechanisms can act in both directions, with the result that the outcome of the balance may be either inhibition or stimulation of tumor growth.