Experimental allergic encephalomyelitis (EAE) is a T(h)1-type cell-mediated autoimmune disease induced by immunization with myelin proteins and mediated by CD4(+) T cells. Although susceptibility to EAE is dependent largely on MHC background, the B10.S strain is resistant to induction of EAE despite sharing the I-A(s) MHC locus with the susceptible SJL strain. Furthermore, NOD mice which spontaneously develop diabetes are susceptible to EAE induction with myelin oligodendrocyte glycoprotein (MOG) 35-55, whereas a MHC congenic strain, III, which also expresses I-A(g7) MHC haplotype does not develop diabetes and is also resistant to EAE induction. We induced EAE in these four strains of mice with MOG peptides 92-106 (for I-A(s) strains) and 35-55 (for I-A(g7) strains) in complete Freund's adjuvant. In the susceptible strains (SJL and NOD) in vitro, there are high levels of IFN-gamma production, whereas the resistant strains (B10.S or III) secreted primarily IL-4/IL-10 and transforming growth factor (TGF)-beta, and had decreased levels of IFN-gamma. When brains from susceptible and resistant mice were examined by immunohistochemical methods for cytokine expression, the brains from resistant mice showed fewer infiltrates which predominantly expressed IL-4 and IL-10 and/or TGF-beta. Brains from NOD and SJL with EAE showed mainly IL-2 and IFN-gamma positive cells. Thus, resistance to MOG induced EAE in B10.S and III mouse strains is related to non-MHC genes and is associated with an altered balance of pro- and anti-inflammatory cytokines both in lymphoid tissue and in the brain following immunization with myelin antigens.