PRF1 and malignant mesothelioma: In addition, asbestos exposure suppressed development of CTL function during MLR, in which CD8+ lymphocytes showed decreases in cytotoxicity and the percentage of intracellular granzyme B. These observations allowed us to speculate that CD8+ lymphocytes in patients with malignant mesothelioma might show a decrease in granzymes or perforin similar to that shown by the MLR culture.