Development of experimental allergic encephalomyelitis during steroid administration. Outcome of neurological immune-mediated disorders under immunosuppressive therapy

Glucocorticoids are frequently employed as immunosuppressive agents. Following clinical reports of occurrence and exacerbation of neurological immune-mediated conditions in patients receiving steroids, we studied the course of experimental allergic encephalomyelitis (EAE) in rats receiving methylprednisolone prior to and during disease induction and after the appearance of clinical signs. High methylprednisolone dose given prior to EAE induction significantly increased disease duration and the number of days at maximal disability. When the drug was given prior to and during the induction phase, both moderate and high doses exacerbated the EAE course. In contrast, treatment with methylprednisolone after the onset of clinical disease had a markedly beneficial effect. Thus, time of initiation, dosage and duration of treatment may differentially affect the course of EAE. Moreover, the natural course of a neurological immune-mediated condition may be worsened when it is triggered while the patient is under steroid treatment.