The effects of cyclophosphamide on antibody dependent cell-mediated cytotoxicity in mice.

The effect of cyclophosphamide (CY) on antibody dependent cell-mediated cytotoxicity (ADCC) was evaluated. The results indicated that a single injection of CY markedly increased ADCC activity of murine splenic cells. This effect was dose dependent and was maximal on day 7 after the drug injection. The number of lymphoid cells in treated mice decreased to approximately 50%; however the percentages of EA rosettes were similar to those of control animals suggesting that the augmented cytotoxic activity was not due to a relative increase in Fc receptor bearing cells. CY treatment also enhanced delayed type hypersensitivity, but suppressed antibody production to sheep red blood cells. The possibility that CY eliminates a suppressor cell subpopulation that normally regulates ADCC levels is discussed.