Specialized dendritic cells induce tumor-promoting IL-10+IL-17+ FoxP3neg regulatory CD4+ T cells in pancreatic carcinoma

The drivers and the specification of CD4 + T cell differentiation in the tumor microenvironment and their contributions to tumor immunity or tolerance are incompletely understood. Using models of pancreatic ductal adenocarcinoma (PDA), we show that a distinct subset of tumor-infiltrating dendritic cells (DC) promotes PDA growth by directing a unique T H -program. Specifically, CD11b + CD103 − DC predominate in PDA, express high IL-23 and TGF-β, and induce FoxP3 neg tumor-promoting IL-10 + IL-17 + IFNγ + regulatory CD4 + T cells. The balance between this distinctive T H program and canonical FoxP3 + T REGS is unaffected by pattern recognition receptor ligation and is modulated by DC expression of retinoic acid. This T H -signature is mimicked in human PDA where it is associated with immune-tolerance and diminished patient survival. Our data suggest that CD11b + CD103 − DC promote CD4 + T cell tolerance in PDA which may underscore its resistance to immunotherapy. Pancreatic ductal adenocarcinoma is characterized by a highly immunosuppressive tumour microenvironment. Here, the authors show that specialized subsets of tumour-infiltrating dendritic cells induce distinct CD4 + T cell programs and specifically identify a CD103 – CD11b + subset which induces tumor-promoting FoxP3 – Type-1 regulatory T cells.