Identification and characterization of polyclonal αβ T cells with dendritic cell properties

An efficient immune response requires coordination between innate and adaptive immunity, which act through cells different in origin and function. Here we report the identification of thymus-derived αβ TCR(+) cells that express CD11c and MHC class II, and require FLT3L for development (T(DC)). T(DC) express genes heretofore found uniquely in T cells or DC, as well as a distinctive signature of cytotoxicity-related genes. Unlike other innate T cell subsets, T(DC) have a polyclonal TCR repertoire andrespond to cognate antigens. However, they differ from conventional T cells in that they do not require help from antigen-presenting cells, respond to TLR-mediated stimulation by producing IL-12 and process and present antigen. The physiologic relevance of T(DC), found in mice and humans, is still under investigation, but the fact that they combine key features of T and DC cells suggests that they provide a bridge between the innate and adaptive immune systems.