The immunopharmacological profile of experimental allergic encephalomyelitis (EAE) in DA rats was compared to that in Lewis rats, which are commonly used for the study of EAE. DA rats showed higher susceptibility to EAE than Lewis rats. The immunological studies indicate that DA rats showed higher humoral and cellular immune response to myelin basic protein (MBP) than Lewis rats. This is probably due to the susceptible T cells to mitogen and autoreactive T cells to MBP in DA rats. In pharmacological studies, cyclosporin A, FK-506 and prednisolone suppressed the development of EAE in both strains in a similar manner. These results suggest the existence of two different types of T cells with respect to the onset of EAE in DA rats: one is highly reactive to mitogen and MBP; the other is regulated by cyclosporin A and FK-506.