Kasheta, MelissaPainter, Corrie A.Moore, Finola E.Lobbardi, RiadhBryll, AlysiaFreiman, EliStachura, DavidRogers, Arlin B.Houvras, YarivLangenau, DavidCeol, Craig J.2018-07-252017Kasheta, M., C. A. Painter, F. E. Moore, R. Lobbardi, A. Bryll, E. Freiman, D. Stachura, et al. 2017. “Identification and characterization of T reg–like cells in zebrafish.” The Journal of Experimental Medicine 214 (12): 3519-3530. doi:10.1084/jem.20162084. http://dx.doi.org/10.1084/jem.20162084.http://nrs.harvard.edu/urn-3:HUL.InstRepos:37298221Regulatory T (T reg) cells are a specialized sublineage of T lymphocytes that suppress autoreactive T cells. Functional studies of T reg cells in vitro have defined multiple suppression mechanisms, and studies of T reg–deficient humans and mice have made clear the important role that these cells play in preventing autoimmunity. However, many questions remain about how T reg cells act in vivo. Specifically, it is not clear which suppression mechanisms are most important, where T reg cells act, and how they get there. To begin to address these issues, we sought to identify T reg cells in zebrafish, a model system that provides unparalleled advantages in live-cell imaging and high-throughput genetic analyses. Using a FOXP3 orthologue as a marker, we identified CD4-enriched, mature T lymphocytes with properties of T reg cells. Zebrafish mutant for foxp3a displayed excess T lymphocytes, splenomegaly, and a profound inflammatory phenotype that was suppressed by genetic ablation of lymphocytes. This study identifies T reg–like cells in zebrafish, providing both a model to study the normal functions of these cells in vivo and mutants to explore the consequences of their loss.en-USBrief Definitive ReportJournal Article2018-07-2510.1084/jem.20162084