The mechanisms responsible for initiating autoimmune diabetes remain obscure. Here, we describe a method for identifying both the ␣-and ␤-chains of the T cell receptor (TCR) from individual pancreatic islet-infiltrating T cells at the earliest stages of disease in nonobese diabetic mice (NOD). Analysis of the TCR repertoire of these early islet infiltrates reveals enrichment for a small subset of TCR sequences. Reconstitution of these TCR in vitro demonstrates that these receptors confer reactivity to islet cells but not to the well characterized autoantigens, glutamic acid decarboxylase (GAD65) and insulin. Thus, autoimmune diabetes in NOD may be initiated by a limited number of antigens distinct from GAD65 and insulin.

We have examined the rate and extent of removal of 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen (HMT) cross-linkable monoadducts and interstrand cross-links from restriction fragments within the amplicon containing the dihydrofolate reductase (DHFR) gene in the Chinese hamster ovary (CHO) cell line B11. The rate and extent of removal of HMT cross-links was significantly greater in an actively transcribed fragment than in a nontranscribed extragenic fragment of similar size. For the 5' half of the DHFR gene, approximately 80% of the HMT cross-links were removed in 8 h, in agreement with results reported by Vos and Wauthier [Vos, J. M., & Wauthier, E. L. (1991) Mol. Cell Biol. 11, 2245-2252, 1991]. However, few cross-links were removed in that period from the nontranscribed fragments, whose 5' end is approximately 7 kb downstream from the DHFR transcription unit and which includes a putative replication initiation site. Even after 24 h, only about 50% of the cross-links had been removed from this fragment. In contrast, both the rate and the extent of removal of cross-linkable HMT monoadducts were similar in the two fragments with 50% of the cross-linkable monoadducts removed in 24 h. Moreover, monoadducts formed in the bulk of the genome were removed in 24 h. Moreover, monoadducts formed in the bulk of the genome were removed at a slightly slower rate and to a lesser extent (30% in 24 hours) than those from either of these specific sequences.(ABSTRACT TRUNCATED AT 250 WORDS)