This information is current as Human Type 1 Diabetes Pancreatic Islets and Spleen at the Onset in TCR Bias of In Vivo Expanded T Cells in

Autoreactive T cells, responsible for the destruction of pancreatic b cells in type 1 diabetes, are known to have a skewed TCR repertoire in the NOD mouse. To define the autoreactive T cell repertoire in human diabetes, we searched for intraislet mono-clonal expansions from a recent onset in human pancreas to then trace them down to the patient's peripheral blood and spleen. Islet infiltration was diverse, but five monoclonal TCR b-chain variable expansions were detected for Vb1, Vb7, Vb11, Vb17, and Vb22 families. To identify any sequence bias in the TCRs from intrapancreatic T cells, we analyzed 139 different CDR3 sequences. We observed amino acid preferences in the NDN region that suggested a skewed TCR repertoire within infiltrating T cells. The monoclonal expanded TCR sequences contained amino acid combinations that fit the observed bias. Using these CDR3 sequences as a marker, we traced some of these expansions in the spleen. There, we identified a Vb22 monoclonal expansion with identical CDR3 sequence to that found in the islets within a polyclonal TCR b-chain variable repertoire. The same Vb22 TCR was detected in the patient's PBMCs, making a cross talk between the pancreas and spleen that was reflected in peripheral blood evident. No other pancreatic monoclonal expansions were found in peripheral blood or the spleen, suggesting that the Vb22 clone may have expanded or accumulated in situ by an autoantigen present in both the spleen and pancreas. Thus, the patient's spleen might be contributing to disease perpetuation by expanding or retaining some autoreactive T cells. T ype 1 diabetes (T1D) is an autoimmune disease defined by the selective destruction of insulin-producing pancreatic b cells, mediated by CD4 + and CD8 + autoreactive T cells (1, 2). Antigenic specificities of intrapancreatic T cells have been mainly defined in the NOD mouse by studies showing that the initial challenge is driven by insulin-specific T cell responses (3, 4), later spreading to GAD and other islet-related autoantigens (5, 6). In contrast, the T cell targets of human T1D have been identified only from the analysis of peripheral T cells, mostly because of the limited availability of human pancreatic tissue. Autoreac-tive T cells were identified in vitro by expansion against insulin, GAD, I-A2, IGRP (7–10), and ex vivo by positive staining with self-peptide–MHC tetramers (11, 12). Although there are no data on the specificity of intrapancreatic T cells in human T1D, phe-notypic analysis of infiltrating lymphocytes …