Unresponsiveness to experimental allergic encephalomyelitis in Lewis rats pretreated with complete Freund's adjuvant

A single injection of complete Freund's adjuvant blended with aluminum hydroxide gel (ALU-CFA) was successfully used to prevent clinical as well as histologic experimental allergic encephalomyelitis (EAE) in Lewis rats for more than 330 days. Adjuvant preparations with Mycobacterium tuberculosis were more potent than those with Mycobacterium butyricum. Neither the removal of the ALU-CFA inoculum nor a splenectomy 1 month after immunization arrested the adjuvant induced unresponsiveness. However cyclophosphamide restored responsiveness in more than half of the treated animals when applied 2 days before the encephalitogenic challenge at a dose of 20 mg/kg. Passive EAE was not prevented by the ALU-CFA pretreatment. The disease was induced by the transfer of 4 X 10(6) T lymphocytes of a cell line reactive against myelin basic protein. This indicates that the adjuvant prevents EAE at the inductive rather than at the effector phase of the autoimmune response.