Conventional CD4+ T cells present bacterial antigens to induce cytotoxic and memory CD8+ T cell responses
Bacterial phagocytosis and antigen cross-presentation to activate CD8+ T cells are principal functions of professional antigen presenting cells. However, conventional CD4+ T cells also capture and kill bacteria from infected dendritic cells in a process termed transphagocytosis (also known as transinfection). Here, we show that transphagocytic T cells present bacterial antigens to naive CD8+ T cells, which proliferate and become cytotoxic in response. CD4+ T-cell-mediated antigen presentation also occurs in vivo in the course of infection, and induces the generation of central memory CD8+ T cells with low PD-1 expression. Moreover, transphagocytic CD4+ T cells induce protective anti-tumour immune responses by priming CD8+ T cells, highlighting the potential of CD4+ T cells as a tool for cancer immunotherapy. ; J.M.G.-G. is supported by the Miguel Servet Program (Instituto de Salud Carlos III; ISCIII) and V.Z. by the ISCIII. This work was supported by grants from the Spanish Ministries of Science and Technology (MICINN; BFU2011-29450 to E.V.) and of Economy and Competitiveness (MINECO; SAF201456716-REDT and BFU2014-59585-R to E.V., SAF2014-55579-R to F.S.M., SAF201347975-R to B.A., SAF2014-58895-JIN to A.C.-A.), the ISCIII (PI14/00526; CP11/00145; CPII16/00022 to J.M.G.-G.), the Fundación Ramón Areces (to J.M.G.-G.), the Madrid regional government (INDISNET-S2011/BMD-2332 to F.S.M.) and the European Research Council (ERC-2011-AdG 294340-GENTRIS to F.S.M.; ERC 2013-AdG 334763 NOVARIPP to B.A.). F.S.M. and J.M.G.-G. are also financed by CIBER Cardiovascular, Spain. ; Sí