Person: Gagnon, Etienne
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Gagnon
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Etienne
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Gagnon, Etienne
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Publication Self-reactive human CD4 T cell clones form unusual immunological synapses(The Rockefeller University Press, 2012) Schubert, David; Gordo, Susana; Sabatino, Joseph J.; Vardhana, Santosh; Gagnon, Etienne; Sethi, Dhruv Kam; Seth, Nilufer P.; Choudhuri, Kaushik; Reijonen, Helena; Nepom, Gerald T.; Evavold, Brian D.; Dustin, Michael L.; Wucherpfennig, KaiRecognition of self–peptide-MHC (pMHC) complexes by CD4 T cells plays an important role in the pathogenesis of many autoimmune diseases. We analyzed formation of immunological synapses (IS) in self-reactive T cell clones from patients with multiple sclerosis and type 1 diabetes. All self-reactive T cells contained a large number of phosphorylated T cell receptor (TCR) microclusters, indicative of active TCR signaling. However, they showed little or no visible pMHC accumulation or transport of TCR–pMHC complexes into a central supramolecular activation cluster (cSMAC). In contrast, influenza-specific T cells accumulated large quantities of pMHC complexes in microclusters and a cSMAC, even when presented with 100-fold lower pMHC densities. The self-reactive T cells also maintained a high degree of motility, again in sharp contrast to virus-specific T cells. 2D affinity measurements of three of these self-reactive T cell clones demonstrated a normal off-rate but a slow on-rate of TCR binding to pMHC. These unusual IS features may facilitate escape from negative selection by self-reactive T cells encountering very small amounts of self-antigen in the thymus. However, these same features may enable acquisition of effector functions by self-reactive T cells encountering large amounts of self-antigen in the target organ of the autoimmune disease.