PRF1 and bronchogenic carcinoma: Additionally, the CMV control population had an earlier age of onset of bronchogenic carcinoma, indicating that a higher population of effector immune cells in the experimental group contributed to a more robust response against malignancy which delayed the onset of bronchogenic carcinoma. The vast increase in natural killer cells leads to more efficient killing of malignant cells through the release of perforins and granzymes and the formation of immune complexes [11].