Immunomodulation and therapeutic characterization of thymosin fraction five.

In this report we describe the characterization of the immunomodulatory efficiency and therapeutic properties of thymosin fraction five (F5). We consistently observed the immunostimulation of T-cell activity in assays of allogeneic mixed lymphocyte response (MLR) and the development of cytotoxic effector cells in an allogeneic mixed lymphocyte tumor response-cell-mediated cytotoxicity assay (MLTR-CMC). No induction of suppressor cell activity was observed. Thymosin F5 also acted successfully as an adjuvant when admixed with irradiated tumor cells. We were unable to demonstrate either NK cell or macrophage activation by thymosin F5. Therapeutic protocols using thymosin F5 and directed against pre-existing experimental and spontaneous metastases, had a significant immunotherapeutic potential.