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      Altered peptide ligands of islet autoantigen Imogen 38 inhibit antigen specific T cell reactivity in human type-1 diabetes.

      Journal of Autoimmunity
      Amino Acid Sequence, Antigens, CD, biosynthesis, Antigens, Differentiation, T-Lymphocyte, Autoantigens, immunology, metabolism, pharmacology, Cytokines, secretion, Diabetes Mellitus, Type 1, Down-Regulation, Epitopes, T-Lymphocyte, drug effects, HLA-DR1 Antigen, Humans, Lectins, C-Type, Ligands, Lymphocyte Activation, Molecular Sequence Data, Peptide Fragments, Receptors, Antigen, T-Cell, Receptors, Interleukin-2, Ribosomal Proteins, T-Lymphocytes

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          Abstract

          Type 1 diabetes, insulin-dependent diabetes mellitus (IDDM) results from autoimmune T cell-dependent destruction of insulin producing beta-cells in the pancreatic islets of Langerhans. T cells from recent-onset IDDM patients specifically proliferate to beta cell membrane Ag enriched fractions, containing the mitochondrial 38 kD islet antigen (Imogen). Recently, we identified a peptide epitope (Imogen p55-70) that is recognized by a 38 kD-specific, Th1 clone from an IDDM patient. In animal models of autoimmune diseases, altered self peptide ligands (APL) have been used effectively in peptide-based immune prevention or therapy. No such APL, however, have been reported so far that can modulate autoreactive T-cell responses in IDDM. Here, we have designed APL of p55-70. These APL efficiently downregulate in vitro activation of the 38 kD-specific Th1 clone induced by either p55-70 or by native beta cell autoantigens. Self peptide reactive T-cell proliferation could be inhibited only when APL and the self peptide were present on the same APC. Unrelated peptides with equal HLA-DR binding affinity were not effective, excluding simple MHC competition as the mechanism for T-cell modulation. APL triggered upregulation of CD69 and CD25 expression, but not T-cell proliferation, TCR down-modulation or T-cell anergy. Thus, the p55-70 APL inhibit beta cell autoantigen-induced activation of an Imogen-reactive T-cell clone derived from an IDDM patient, by acting as partial TCR agonists that inhibit TCR down-modulation. Copyright 1998 Academic Press

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