Inhibition of the development of suppressor cells in culture by 4-hydroperoxycyclophosphamide

Abstract

Abstract The effect of 4-hydroperoxycyclophosphamide (4-OOH-CYP), an in vitro active form of cyclophosphamide, on the development of the suppressor cells that modulate the cytotoxic T cell response to alloantigens was investigated. Treatment of spleen cells with 4-OOH-CYP inhibited the development of suppression in culture but did not prevent the development of cytotoxicity to alloantigens. The effects of 4-OOH-CYP pretreatment at a concentration of 15 microM were found to be specific for Thy-1.2+ suppressor cells and inhibited suppressor function in a dose-dependent fashion (ED50 = 7.86 ± 0.29 microM). The 4-OOH-CYP-sensitive suppressor precursor population is most likely Lyt-1+2+ whereas differentiated suppressor cells are of the Lyt-1-2+ phenotype. These results demonstrate that 4-OOH-CYP can be utilized in vitro to separate functionally distinct immunoregulatory T cell subsets.