Resistance of T suppressor cells to cyclophosphamide administration in total-lymphoid-irradiated mice

The effect of administration of cyclophosphamide (Cy) on the susceptibility of mice to tolerance induction and its influence on the rate of induced T suppressor cells in antigen-specific and nonspecific systems was assessed using mice that had undergone total lymphoid irradiation (TLI). Tolerance to bovine serum albumin (BSA) was induced in adult mice conditioned by a short course of fractionated total lymphoid irradiation with an injection of nondeaggregated BSA; Cy was administered upon termination of TLI, two days prior to administration of the tolerizing antigen. Susceptibility to tolerance induction and rate of induced T suppressor cells were assessed one month later. Cy-treated TLI mice and mice treated with TLI alone did not respond to a challenge with DNP-BSA in complete Freund’s adjuvant, whereas a good response was obtained to an unrelated protein antigen. The induced T suppressor cell rate was measured by inhibition of a secondary anti DNP-BSA response in an adoptive transfer system. The rate of non-antigen-specific T suppressor cells was measured by inhibition of the mixed leukocyte reaction with Concanavalin A-induced T suppressor cells obtained from spleen cells of TLI-treated, or Cy-treated mice, or those given both treatments. The results reveal that Cy treatment of TLI-conditioned mice does not reduce the rate of induced of T suppressor cells in antigen-specific and antigen-nonspecific systems.