Cyclophosphamide-Induced Tolerance to Equine γ Globulin and to Equine-Anti-Mouse-Thymocyte Globulin in Adult Mice

Adult mice were made tolerant to equine γ globulin (EqGG) and to equine-anti-mouse-thymocyte globulin (ATG) by injection of EqGG (deaggregated, heat-aggregated, or in Freund's adjuvant) or ATG followed by cyclophosphamide (CY). Injection of deaggregated EqGG alone resulted in only “marginal” tolerance, whereas the other injections alone were immunogenic. The resulting tolerance could be shown to be of long duration without further antigen or drug injections. Relationships between the dose of CY required for tolerance induction and the timing of the drug in relation to antigen administration were established.