Skewed T-Cell Receptor Usage and Junctional Heterogeneity Among Isletitis αβ and γδ T-cells in Human IDDM

Because of anatomical limitations, molecular characterization of islet-inflammatory T-cells in human insulin-dependent diabetes mellitus (IDDM) has remained elusive. We have isolated isletitis T-cells from pancreas graft biopsies of two patients (syngeneic and allogeneic, respectively) shortly after onset of recurrent IDDM and have characterized their repertoire by sequencing T-cell receptor (TcR)-specific cDNAs. Histopathological analysis of the grafts revealed selective β-cell loss and isletitis characteristic of recurrent disease with no evidence of chronic inflammation or rejection. Most of the in vivo-activated isletitis T-cells were CD8+TcRαβ⁺ and CD4⁻CD8⁻TcRγδ+ in both patients. Comparison of the different TcRα,β,γ, and δ sequences revealed V(D)J junctional heterogeneity but skewed TcR usage within patients. Eighth of 13 different isletitis TcRβ sequences (19 of 26 cDNAs) from the syngeneic graft of patient 1 were Vβ3⁺, as opposed to only 1 of 31 peripheral TcRβ sequences (1 of 31 cDNAs) (61.5 vs. 3.2%, P < 0.0001). Of the 19 different isletitis TcRα clonotypes of this patient (24 of 42 cDNAs), 5 were Vα14⁺. The isletitis TcRβ clonotypes of the human leukocyte antigen-identical allogeneic graft of patient 2 showed selective Jβ, but not Vβ, gene usage. Two of three predominant isletitis clonotypes of patient 2 were Vα22⁺ (19 of 28 cDNAs) and the other (5 of 28 cDNAs) was also Vα14⁺. As opposed to peripherl γδ T-cell, which usedall Vγ and Vδ gene families, isletitis γδ T-cells only used VγI, Vγ2, Vδ1, and Vδ2 (patient 1) or VγI, Vγ2, Vγ3, and Vδ1 (patient 2) genes. These data are compatible with preferential recruitment of certain CD8⁺ and CD4⁻CD8⁻ T-cells to islets on the basis of TcR-V and/or J gene usage, which varies among patients, but favors a response against multiple target major histocompatibility complex/peptide complexes.