Regulation of the effector stages of experimental autoimmune encephalomyelitis via neuroantigen-specific tolerance induction: II. Fine specificity of effector T cell inhibition

Ag-specific tolerance induced by the i.v. administration of splenocytes coupled with mouse spinal cord homogenate, containing a mixture of myelin Ag, dramatically inhibits development and expression of clinical and histologic signs of both active and adoptive forms of relapsing experimental autoimmune encephalomyelitis (R-EAE) in the SJL/J host. Here we examined the dose-dependency, route of tolerogen administration, and fine neuroantigen specificity of inhibition of adoptive R-EAE. Expression of clinical R-EAE induced by a polyclonal population of bovine myelin basic protein (MBP)-specific effector T cells was dramatically inhibited in a dose-dependent manner following the i.v., but not s.c. or i.p., injection of MBP-coupled splenocytes. The exquisite Ag specificity of the inhibition was evident by the observation that splenocytes coupled with intact bovine MBP or species variants of MBP homologous with bovine MBP within the major encephalitogenic region (amino acids 84-104), but not with proteolipid protein or mouse kidney homogenate, were able to suppress disease expression. Splenocytes coupled with the MBP_84-104 peptide, containing a nested set of the major SJL/J encephalitogenic epitopes, completely inhibited peptide-specific T cell responses, but only partially inhibited the expression of disease transferred by T cells specific for intact MBP, suggesting the participation of T cell responses specific for additional MBP determinants in disease pathogenesis. However, splenocytes coupled with previously identified minor SJL/ J encephalitogenic epitopes (MBP_91-104 or MBP_17-27), or with the Lewis rat major encephalitogenic epitope (MBP_68-86). did not suppress disease expression. Collectively, the results demonstrate that MBP_84-104-specific T cells and T cells specific for an as yet unidentified MBP epitope(s) contribute to the pathology of R-EAE. In addition, the results demonstrate that peptide-specific tolerance induction appears to have potential for the treatment of T cell-mediated inflammatory diseases.