Role of class II MHC bound antigenic peptide in the pathogenesis of inflammatory bowel disease.

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Isolation of antigenic peptides from the MHC-groove has contributed to the understanding of T cell immune responses. We already reported antigenic peptides isolated from human intestinal HLA-DR grove contained various enteral antigens.However, naturally bound peptide ligands for HLA-DP have yet to be reported in clinical samples. We examined antigenic peptides bound to the HLA-DP as well as HLR-DR groove in human intestine by ion-trap tandem mass spectrometry equipped with online reverse-phase high performance liquid chromatography. We detected 7 HLA-DR associated peptides and 10 HLA-DP associated peptides from 4 controls, 4 patients with ulcerative colitis, and 9 patients with Crohn's disease. The calculated molecular masses (m/z) of these peptides reangesd from 1430.7 to 2987.3 and 1212.6 to 2105.0 representing 15 to 26 and 15 to 18 amino-acid residues from HLA-DR and HLA-DP associated peptides, respectively. Most of these parent proteins were exogenous proteins including Escherichia coli, and Carnorhabditis elegans. The present results suggest that in vivo antigen processing by antigen-presenting cells and T lymphocytes in human intestine are participated with exogenous antigen presentation.