Combined effects of cyclophosphamide and thymostimulin treatment on the in vitro natural killer and candidacidal activity of murine spleen cells.

Two different natural cell-mediated cytotoxic reactions (lysis of YAC-1 and killing of Candida albicans) in vitro were studied in mice undergoing treatment with cyclophosphamide (Cy), thymostimulin (TP-1) or a combination of both. Enhancing effects followed the combination regime in the microbial natural cell-mediated cytotoxicity assay, whereas in the NK assay the effect of TP-1 appeared to be antagonistic to that of Cy. The possible mechanisms involved are discussed.