DIRECT BINDING OF AUTOIMMUNE-DISEASE RELATED T-CELL EPITOPES TO PURIFIED LEWIS RAT MHC CLASS-II MOLECULES

New strategies applied in the treatment of experimental autoimmune dis ease models involve blocking or modulation of MHC - peptide - TCR inte ractions either at the level of peptide - MHC interaction or, alternat ively, at the level of T cell recognition. In order to identify useful competitor peptides one must be able to assess peptide - MHC interact ions. Several well described autoimmune disease models exist in the Le wis rat and thus this particular rat strain provides a good model syst em to study the effect of competitor peptides. So far no information h as been available on the peptide binding characteristics of the Lewis rat MHC class II RT1.B(I) molecule. We have now developed a biochemica l binding assay which enables competition studies in which the relativ e MHC binding affinity of a set of non-labelled peptides can be assess ed while employing detection of blotinylated marker peptides by chemil uminescence. The assay is sensitive and specific. We have used this as say to determine the binding characteristics of several disease associ ated T cell determinants and their sequence analogues in the Lewis rat . Notably, most of the autoimmune disease associated peptide sequences tested were found to be intermediate to poor binders. Single amino ac id substitutions at defined positions were sufficient to turn certain peptides into good binders. These results are relevant to the design o f competitor peptides in the treatment of experimental autoimmune dise ases.