Thymosin alpha 1 potentiates interleukin 2-induced cytotoxic activity in mice.

We have investigated the effects of interleukin 2 (IL-2) on cytotoxic activity of spleen lymphocytes, from normal and cyclophosphamide (200 mg/kg) or B-16 melanoma suppressed mice, after in vitro or in vivo pretreatment with thymosin alpha 1 (TA1). The results of this study indicate that pretreatment in vitro (100 ng/ml for 1 hr) or in vivo (200 micrograms/kg/day for 4 days) with thymosin alpha 1 (TA1), significantly increased the IL-2 (from 100 to 500 U/ml) in vitro induced cytotoxic activity of spleen lymphocytes, collected from both normal and cyclophosphamide and tumor-suppressed animals, against both YAC-1 (NK sensitive) and MBL-2 (NK resistant) cell lines. The potential use in combination of these two different biological response modifiers, useful in enhancing the immunological responses to IL-2 of lymphocytes, may provide a novel model of immunotherapeutic intervention in cancer.