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  • Title: Thymic positive selection and peripheral activation of islet antigen-specific T cells: separation of two diabetogenic steps by an I-A(g7) class II MHC beta-chain mutant.
    Author: Kanagawa O, Vaupel BA, Xu G, Unanue ER, Katz JD.
    Journal: J Immunol; 1998 Nov 01; 161(9):4489-92. PubMed ID: 9794372.
    Abstract:
    The diabetes-susceptible class II MHC genes (in human and mouse) share unique nonaspartic acid residues at position 57 of the class II beta-chain. Transgenic expression of a mutant I-A(g7), substituting histidine and serine at position 56 and 57 of beta-chain with proline and aspartic acid (I-A(g7)PD), respectively, inhibits diabetes development in the nonobese diabetic mouse model. Here, we demonstrate that immature thymocytes expressing a diabetogenic islet Ag-specific transgenic TCR are positively selected by I-A(g7)PD class II MHC to give rise to mature CD4+ T cells. However, splenic APCs expressing the same I-A(g7)PD fail to present pancreatic islet Ag to mature T cells bearing this diabetogenic TCR. These results indicate that nonaspartic acid residues at position 57 of class II MHC beta-chain is important for diabetogenic CD4+ T cell activation in the periphery but is not essential for the formation of a diabetogenic T cell repertoire in the thymus.
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