Amplification of eosinophilia by melatonin during the immunotherapy of cancer with interleukin-2.

Eosinophilia, which occurs during IL-2 immunotherapy, has appeared to be due to an enhanced secretion of IL-5 and to be associated with a clinical response. Since our previous experimental studies showed that the pineal hormone MLT potentiates IL-2 efficacy, a study was started to evaluate the influence of a concomitant MLT administration on IL-2-induced eosinophilia. The study included 30 advanced solid tumor patients, 16 of whom received IL-2 alone (6 million IU/day) and the other 14 IL-2 plus MLT (10 mg/day orally at 8.00 P.M.). Eosinophil mean number was significantly enhanced during both treatments, but its increase in patients receiving IL-2 plus MLT was significantly higher than that seen in patients treated with IL-2 alone. These results show that MLT may enhance IL-2-induced eosinophilia, by suggesting that T helper lymphocyte- type 2, which is the source of IL-5, may be the target cell for MLT action.