Identification of MHC Class II-Restricted Peptide Ligands, Including a Glutamic Acid Decarboxylase 65 Sequence, that Stimulate Diabetogenic T Cells from Transgenic BDC2.5 Nonobese Diabetic Mice

摘要

Nonobese diabetic (NOD) mice spontaneously develop insulitis and destruction of pancreatic islet f:J cells similar to type 1 diabetl mellitis in humans. Insulitis also occurs in the BDC2.5 TCR transgenic line of NOD mice that express the rearranged TCR a- an f:J-chain genes of a diabetogenic NOD CD4 T cell clone. When activated with syngeneic islet cells in culture, BDC2.5 T cell adoptively transfer disease to NOD recipients, but the identity of the islet cell Ag responsible for pathogenicity is not known. T characterize the autoantigen(s) involved, BDC2.5 T cells were used to screen a combinatorial peptide library arranged in positional scanning format. We identified more than 100 decapeptides that stimulate these T cells at nanomolar concentrations they are then capable of transferring disease to NOD-scid mice. Surprisingly, some of the peptides include sequences similar (8 o 10 residues) to those found within the 528-539 fragment of glutamic acid decarboxylase 65. Although this 12-mer glutamic acil decarboxylase 65 fragment is only slightly stimulatory for BDC2.5 T cells (ECso > 100 lA-M), a larger 16-mer fragment, 526-54] shows activity in the low micromolar range (ECso = 2.3 lA-M). Finally, T cells from prediabetic NOD mice respond spontaneousl to these peptide analogs in culture; this finding validates them as being related to a critical autoantigen involved in the etiolog of spontaneous diabetes and indicates that their further characterization is important for abetter understanding of underlyin: disease mechanisms.