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 cl inical response. Since our previous experimental studies showed that t he pineal hormone MLT potentiates IL-2 efficacy, a study was started t o evaluate the influence of a concomitant MLT administration on IL-2-i nduced eosinophilia. The study included 30 advanced solid tumor patien ts, 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 i n 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 lym phocyte- type 2, which is the source of IL-5, may be the target cell f or MLT action.