Analysis of TCR/HLA/ peptide interaction and investigation of etiology of autoimmune diseases

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In the previous studies, we discovered assedations between specific HLA class II alleles and susceptibility to autoimmune diseases, and examined binding peptide motifs of disease-associated HLA class II molecules. In this study, to clarify the mechanisms of the disease-association of specific HLA alleles, we carried out the following researches. Identification of self peptides recognized by disease-related autoreactive T cell clones. We established many auto-antigen specific CD4^+ T cell clones from Asian type multiple sclerosis (MS) and anti-phosopholipid antibody syndrome (APS) patients. We identified many epitopes derived from self antigens and restricting HLA class II molecules, and examined the cytokines produced by the T cell clones. In addition, we searched for the target autoantigen of Vogt -Koyanagi-Harada disease (VKH), an autoimmune diseas e in which inflammatory disorders occur in multiple organs containing melanocytes. By SEREX method, we identified LEDGF (Lens Epithelial … More Cel l Derived Growth Factor) and UACA (Uveal Autoantigen with Coiled coil domains and Ankyrin repeats) as candidates for the target antigen. 2) Establishment of a method to identify cross-reactive epitopes recognized by disease-related autoreactive T cells.We established an expression cloning system to identify epitopes for CD4^+ T cell clones. Using this system, we examined the pattern of epitopes cross-recognized by two CD4^+ T cell clones established from Type I diabetes patients and specific to glutamate decarboxylase 65 (GAD65). Based on this information, we identified several mimicry epitopes of microbial antigen origin. 3) Analysis of T cell response induced by analogues of agonistic epilopes.We generated series of L cell transfectants expressing complexes of HLA-DR4 (DRB1^*0406) and agonist or partial agonist peptides in various densities. Using the transfectants, we discovered that a certain partial agonist peptide, when presented in a very high density, can induce T cell response in a similar magnitude as a full agonist peptide, andthat the T cell response is not accompanied by phosphorylation of ZAP-70 and LAT. We identified unique profiles of produced cytokines, down-modulation of TCR, and intracellular signaling events associated with this unique T cell response. Less