The influence of cyclosporin A on alloantibody responses in inbred rats: provisional evidence for a serum factor with antiidiotypic activity.

The effect of cyclosporin A (CsA) on alloantibody synthesis has been investigated in inbred F344 (RTl1v1) rats receiving weekly transfusions of DA (RT1a) rat whole blood. Whereas repeated transfusion resulted in a persistent alloantibody response (Group I) administration of CsA (15 mg/kg/day) from either days 0-7 (Group II), days 8-49 (Group III) or days 15-49 (Group IV) resulted in the eventual suppression of alloantibody responses before the end of the experiment on day 49. Antiidiotypic activity was detected in sera obtained on day 49 from animals in Groups II, III and IV, shown to reside in the serum fraction of apparent molecular mass of between 150 and 170 kD and to be specific for alloantisera raised in F344 and the closely related LEW (RTl1) rats but not the unrelated AO (RTlu) strain. These experiments suggest that the immunosuppressive action of CsA may, in part, be due to the development of anti-idiotypic activity whose nature remains to be more fully characterized.