Emerging autoimmunity (epitope-spreading) generated as a consequence of myelin damage is suggested to underlie the relapses in multiple sclerosis (MS). Myelin oligodendrocyte glycoprotein (MOG 8-21) induces relapsing EAE in ABH mice characterized by broadening of the autoimmune reportoire. Despite epitope spreading tolerance to the priming antigen, but not emerging epitope reactivities, resulted in long-term inhibition of clinical relapse. In contrast, spinal cord homogenate induced EAE was dominated by a proteolipid protein (PLP 56-70) autoreactivity despite the plethora of CNS antigens in the immunogen. This data suggests that during relapsing-remitting demyelinating disease the pathogenic process is dominated by the initiating antigen, with only a minor role played by emerging T-cell populations. These findings may have important implications for the efficacy of antigen-based immune therapies in autoimmune disorders.