Different susceptibility of various T-dependent immune reactions after in vivo administration of cyclosporin A in mice.

The suppressive effects of Cyclosporin A (Cs A) on various types of T-dependent immune reactions, including delayed footpad reaction (DFR), plaque-forming cells (PFC), and cell-mediated cytolysis (CMC), were compared after intramuscular (i.m.) administration of this drug into mice immunized intraperitoneally (i.p.) with chicken erythrocytes (CRBC). A single injection with a high dosage of 500 mg/kg, at the time of the antigen administration suppressed only the PFC, but not the DFR and CMC. Three low dosage injections of 50 mg/kg the day before, on, and after the immunization also induced suppression of PFC. In this treatment, a dose of 100 mg/kg had a marked affect on PFC and CMC. DFR was slightly suppressed with a dose of 100 mg/kg, but markedly so with a dose of 200 mg/kg. This indicates that PFC is very sensitive to Cs A, CMC is moderately sensitive, and DFR is relatively resistant. The injections of Cs A close to the time of antigen administration are more effective than before or after. Thus it is indicated that the 3 types of reactions differ in their susceptibility to Cs A. It might be speculated that the susceptibility to Cs A varies among the types of T cells responsible for these 3 immune reactions, although this is only one of several possibilities.