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OBJECTIVE--Type 1 diabetes is mediated by T-cell entry into pancreatic islets and destruction of insulin-producing β-cells. The relative contribution of T-cells specific for different autoantigens is largely unknown because relatively few have been assessed in vivo. RESEARCH DESIGN AND METHODS--We generated mice possessing a monoclonal population of T-cells expressing 1 of 17 T-cell receptors (TCR) specific for either known autoantigens (GAD65, insulinoma-associated protein 2 (IA2), IA2β/phogrin, and insulin), unknown islet antigens, or control antigens on a NOD.scid background using retroviral-mediated stem cell gene transfer and 2A-linked multicistronic retroviral vectors (referred to herein as retrogenic [Rg] mice). The TCR Rg approach provides a mechanism by which T-cells with broad phenotypic differences can be directly compared. RESULTS--Neither GAD- nor IA2-specific TCRs mediated T-cell islet infiltration or diabetes even though T-cells developed in these Rg mice and responded to their cognate epitope. IA2β/ phogrin and insulin-specific Rg T-cells produced variable levels of insulitis, with one TCR producing delayed diabetes. Three TCRs specific for unknown islet antigens produced a hierarchy of insulitogenic and diabetogenic potential (BDC-2.5 > NY4.1 > BDC-6.9), while a fourth (BDC-10.1) mediated dramatically accelerated disease, with all mice diabetic by day 33, well before full T-cell reconstitution (days 42-56). Remarkably, as few as 1,000 BDC-10.1 Rg T-cells caused rapid diabetes following adoptive transfer into NOD.scid mice. CONCLUSIONS--Our data show that relatively few autoantigen-specific TCRs can mediate islet infiltration and β-cell destruction on their own and that autoreactivity does not necessarily imply pathogenicity. Diabetes 57:1321-1330, 2008 [ABSTRACT FROM AUTHOR]

Summary: Type 1 diabetes is a T cell-mediated autoimmune disease, characterized by lymphocytic infiltration of the pancreatic islets. It is currently thought that islet antigen specificity is not a requirement for islet entry and that diabetogenic T cells can recruit a heterogeneous bystander T cell population. We tested this assumption directly by generating T cell receptor (TCR) retrogenic mice expressing two different T cell populations. By combining diabetogenic and nondiabetogenic or nonautoantigen-specific T cells, we demonstrate that bystander T cells cannot accumulate in the pancreatic islets. Autoantigen-specific T cells that accumulate in islets, but do not cause diabetes, were also unaffected by the presence of diabetogenic T cells. Additionally, 67% of TCRs cloned from nonobese diabetic (NOD) islet-infiltrating CD4+ T cells were able to mediate cell-autonomous islet infiltration and/or diabetes when expressed in retrogenic mice. Therefore, islet entry and accumulation appears to be a cell-autonomous and tightly regulated event and is governed by islet antigen specificity. [Copyright &y& Elsevier]