Peri-islet infiltrates of young non-obese diabetic mice display restricted TCR beta-chain diversity.

Abstract

To define the clonal diversity of autoreactive T cells associated with the induction of type 1 diabetes, we characterized TCR expression in the earliest detectable islet infiltrates of non-obese diabetic (NOD) mice. The islets of young NOD females were examined for V beta and J beta germ-line gene usage and V(D)J beta junctional sequence diversity. The results from 7-wk-old mice corroborate prior studies demonstrating that the T cell repertoire of islet infiltrates diversifies early in the inflammatory process. In contrast, examination of 4-wk-old NOD mice showed that TCR-beta expression in the peri-islet infiltrates was restricted both in V beta and J beta gene utilization and, most significantly, in V(D)J junctional sequence diversity. Islet-infiltrating T cells from young mice included V beta 3+ T cells, despite the presence of a mammary tumor virus-3-associated superantigen that deletes the majority of immature V beta 3+ thymocytes in NOD mice. Few other TCR V beta types were repeatedly detectable in early stage infiltrates. V(D)J junctional sequence diversity was evaluated in cDNA libraries made from the islets of young NOD mice. Analysis of these clones revealed limited junctional CDR3 diversity in early-infiltrating T cells, as compared with lymph node T cell libraries. Evaluation of TCR expression in individual islets revealed CDR3 sequence conservation between animals and among islets from a single animal. These results suggest that T cells bearing limited TCR-beta-chain diversity contribute to the inductive phases of autoimmune diabetes.