Effector T cells have the capability of recognizing and killing cancer cells. However, whether tumors can become immune resistant through exclusion of effector T cells from the tumor microenvironment is not known. By using a tumor model resembling non-T cell-inflamed human tumors, we assessed whether adoptive T cell transfer might overcome failed spontaneous priming. Flow cytometric assays combined with intra-vital imaging indicated failed trafficking of effector T cells into tumors. Mechanistically, this was due to the absence of CXCL9/10, which we found to be produced by CD103+ dendritic cells (DCs) in T cell-inflamed tumors. Our data indicate that lack of CD103+ DCs within the tumor microenvironment dominantly resists the effector phase of an anti-tumor T cell response, contributing to immune escape.
