The thymus generates major histocompatibility complex (MHC)-restricted αβT cells that only recognize antigenic ligands in association with MHC or MHC-like molecules. We hypothesized that MHC specificity might be imposed on a broader αβTCR repertoire during thymic selection by CD4 and CD8 coreceptors that bind and effectively sequester the tyrosine kinase Lck, thereby preventing T cell receptor (TCR) signaling by non-MHC ligands that do not engage either coreceptor. This hypothesis predicts that, in coreceptor-deficient mice, αβ thymocytes would be signaled by non-MHC ligands to differentiate into αβT cells lacking MHC specificity. We now report that MHC-independent αβT cells were indeed generated in mice deficient in both coreceptors as well as MHC ("quad-deficient" mice) and that such mice contained a diverse αβT cell repertoire whose MHC independence was confirmed at the clonal level. We conclude that CD4 and CD8 coreceptors impose MHC specificity on a broader αβTCR repertoire during thymic selection by preventing thymocytes from being signaled by non-MHC ligands. © 2007 Elsevier Inc. All rights reserved.
Van Laethem, F., Sarafova, S. D., Park, J. H., Tai, X., Pobezinsky, L., Guinter, T. I. I., … Singer, A. (2007). Deletion of CD4 and CD8 Coreceptors Permits Generation of αβT Cells that Recognize Antigens Independently of the MHC. Immunity, 27(5), 735–750. https://doi.org/10.1016/j.immuni.2007.10.007