Intravenous administration of neuroantigen-coupled syngeneic splenocytes is an efficient regimen for Ag-specific regulation of relapsing experimental autoimmune encephalomyelitis (R-EAE) at the effector level of the disease process. Treatment of SJL/J mice with splenocytes coupled with mouse spinal cord homogenate (MSCH) or myelin proteolipid protein after immunization with mouse spinal cord homogenate in CFA, but before the onset of clinical signs specifically inhibited the expression of neuroantigen-specific delayed-type hypersensitivity responses and significantly suppressed the onset, severity, and the duration of clinical and histologic signs of R-EAE. In contrast, the clinical course of R-EAE was not affected by tolerization with myelin basic protein-coupled splenocytes, indicating that proteolipid protein-specific responses play the major role in active MSCH-induced R-EAE. To ensure a physical and temporal separation between the inductive and effector stages of the disease process, we also examined the effects of neuroantigen-coupled splenocytes on adoptive R-EAE. Treatment of recipient mice with MSCH-coupled splenocytes up to 6 days after the transfer of MBP-primed lymph node cells induced a dose-dependent, profound, and long-lasting inhibition of clinical and histologic signs of adoptive R-EAE. The demonstration that splenocytes coupled with a heterogeneous mixture of neuroantigens (i.e., MSCH) can inhibit established immune responses suggests that this methodology has potential for regulating ongoing immune responses associated with autoimmune disorders or chronic graft rejection in which the specific (auto)Ag has yet to be identified.