Characterization of cyclophosphamide-induced suppressor cells.

Spleen cells from mice injected with cyclophosphamide (200 mg/kg body weight) suppress the secondary immunoglobulin (IgG antibody response of memory cells to a T-dependent antigen, dinitrolphenylated (DNP) human gamma globulin, in Millipore diffusion chambers. Characterization of the suppressor cell revealed that it was nylon wool nonadherent, insensitive to treatment with anti-Thy 1.2 or anti-Ig serum plus C, found in spleen but not thymus or lymph nodes, generated in thymectomized mice and nude mice, and heat-sensitive. Because of these unique characteristics, it was concluded that the suppressor cell was not a typical B cell, T cell, or macrophage. The suppressor cell was found to be regulated, i.e., inhibited, by a T cell found in the thymus and possibly the lymph nodes of normal mice. The suppressor cells may have biological significance in relation to development of self-tolerance.