HLA-DQ-Restricted, Islet-Specific T-Cell Clones of a Type I Diabetic Patient: T-Cell Receptor Sequence Similarities to Insulitis-Inducing T-Cells of Nonobese Diabetic Mice

We established a T-cell line and 20 CD⁴⁺ T-cell clones from the peripheral blood lymphocytes of a type I diabetic patient using a membrane preparation of a rat insulinoma cell line (beta membrane antigen [BMA]) as a source of antigen. The T-cell line and three selected clones proliferated specifically to stimulation with BMA and to membranes prepared from human islets, rat pancreas, and NOD pancreas, but not to control antigens. Proliferationinhibition studies using human leukocyte antigen (HLA)-specific monoclonal antibodies revealed HLA-DQw1-restricted recognition of BMA. An analysis of the T-cell receptor (TCR) repertoire of the T-cell line after 8 and 40 days of culture showed a prominent usage of the Val and Vα12 gene families. Although sequencing of the TCR Vα and Vβ chains of the three clones demonstrated that each used different Va and V(J gene segments, structural similarities were found in complementary-determining region 3 (CDR3), the region that is postulated to interact with the peptide component of the TCR ligand. When we compared these TCR sequences with published sequences of disease-inducing T-cells of NOD mice, highly related TCR Vβ families were detected. Furthermore, stretches of identical amino acids within the CDR3 region were found between two pairs of human and mouse T-cells. If one considers the species differences in TCR genes and sequence differences in the restriction elements for these cells (HLA-DQ vs. H-2I-A^nod), these sequence similarities are striking and may be useful for pinpointing T-cells of primary importance in the development of disease.