Participation of cyclophosphamide-sensitive T cells in graft-vs-host reactions.

Cyclophosphamide (CY)3 is toxic for a population of mouse T cells which is active in graft vs host (GVH) responses. This observation contrasts with previous reports which indicate that treatment of mice with CY regimens, similar to those used in this study, enhances the reactivity of T cells which mediate delayed type hypersensitivity to sheep red blood cells. The GVH-inducing capacity of T cells is not altered by removal of B cells by nylon wool columns. We suggest that CY-sensitive T cells may be "regulatory cells," and that the effect they have depends on, among other things, the nature of the stimulating antigen to which the cells are responding and/or the assay used for study.