[Enhancement of immune response by an antitumor agent, cyclophosphamide]

Cyclophosphamide (CY) is an agent with one of the broadest antitumor spectra in cancer chemotherapy. CY was chosen because its effectiveness in tumor immunity in combination with other agents (BCG or FPL) had been shown in our previous experiments. The effect of CY on the immuno-regulatory system is diverse, depending on a multitude of factors including the type of immune response measured, the antigen, the dose of the drug, the time of its administration in relation to antigen, etc. Thus, we investigated the effect of CY on suppressive factors using an adoptive transfer approach in both DTH reaction and tumor immunity. The results indicated that CY would eliminate suppressor cells regulating cellular responses in DTH reaction and tumor immunity in a variable manner.