The role of the adrenal in relapses of experimental allergic encephalomyelitis.

Adrenalectomy shortly after onset of clinical signs of experimental allergic encephalomyelitis (EAE) was uniformly lethal to rats within 2 days. If adrenalectomy was postponed until the third to fifth day of signs, most of the rats survived and experienced a complete or incomplete remission followed by a relapse. The success of adrenalectomy in inducing relapses suggests that spontaneous relapses in EAE are related to adrenal homeostatic mechanisms whereby paralysis, nonspecific stress, increased corticosteroids, immunosuppression, recovery from paralysis, decreased stress, corticosteroids and reimmunization follow each other in logical order. However, the failure of adrenalectomy to induce relapses in EAE produced with aqueous inoculum or by passive transfer with lymphoid cells suggests that relapses are related to the persistent antigenic depot from water-in-oil inocula, rather than being an inherent part of the immunopathologic process.