Treatment of experimental allergic encephalomyelitis in rats with total body irradiation and syngeneic BMT.

Experimental allergic encephalomyelitis (EAE) was induced in Buffalo rats by immunization with syngeneic spinal cord homogenate in complete adjuvant. EAE, an autoimmune disease of the central nervous system (CNS), is regarded as a model for multiple sclerosis. When severe paresis had developed, rats were treated with high-dose total body irradiation (TBI) and transplanted with syngeneic BM from healthy donors. Nine Gy TBI followed by syngeneic BMT greatly accelerated recovery of paresis compared with untreated controls. In 6-33% of the treated animals a relapse of EAE was observed shortly after treatment. Reimmunization 20 days after treatment, resulted in a relapse in 12-44% of the rats. Employing the maximally tolerated dose of TBI (10 Gy) did not significantly alter the incidence of spontaneous or induced relapses. Furthermore, it was shown that irradiation of the CNS only was not sufficient for the induction of complete regression of paresis. The origin of the cells responsible for these relapses is discussed, as is the importance of reimmunization in evaluating the effect of treatment of experimental autoimmune disease.