Autoantigen-induced focusing of vβ13+ T cells precedes onset of autoimmune diabetes in the LEW.1WR1 rat

Abstract

The earliest events leading to autoimmune type 1 diabetes (T1D) are not known in any species. A T-cell receptor (TCR)-variable region, TCR-Vb13, is required for susceptibility to autoimmune diabetes in rats, and selective depletion of Vb13+ T cells with an allele-specific monoclonal antibody prevents disease in multiple rat strains. To investigate the role of Vb13 early in diabetes, we examined islet T-cell transcripts in susceptible (LEW.1WR1) and resistant (LEW.1W and Wistar Furth) strains induced with polyinosinic: polycytidylic acid. Vb13+ T cells displayed antigenic focusing in LEW.1WR1 islets 5 days postinduction and were characterized by a substantial decrease in complementarity determining region 3 diversity. This occurred prior to significant islet T-cell accumulation (day 7) or frank diabetes (days 10-14). Vb13+ transcripts increased in LEW.1WR1 islets during diabetes progression, but not in resistant rats. We also analyzed transcript clonality of rat TCR-Va5, an ortholog of the dominant TCR-Va chain found on insulin B:9-23-reactive T cells in nonobese diabetic rat islets. We observed clonal expansion of Va5+ transcripts in prediabetic LEW.1WR1 islets, suggesting that rat Va5 is also an important component of islet autoantigen recognition. These data provide additional evidence that genome-encoded TCR sequences are important determinants of genetic susceptibility to T1D. © 2014 by the American Diabetes Association.