SRP410899 PRJNA907381 GSE219197 CD5 expression by dendritic cells directs T cell immunity and sustains immunotherapy responses The induction of proinflammatory T cells by dendritic cell (DC) subtypes is critical for anti-tumor responses and effective immune checkpoint blockade (ICB) therapy. Here we show that human CD1c+CD5+ dendritic cells are reduced in melanoma-affected lymph nodes, with CD5 expression on DCs correlating with patient survival. Activating CD5 on DCs enhanced T-cell priming and improved survival after immune checkpoint blockade therapy. CD5+ DC numbers increased during ICB treatment, and low IL-6 levels promoted their de novo differentiation. Mechanistically, CD5 expression by DCs was required to generate optimally protective CD5hi T helper and CD8+ T cells; further, deletion of CD5 from T cells dampened tumor elimination in response to ICB therapy in vivo. Thus, CD5+ dendritic cells are an essential component of optimal immune checkpoint blockade therapy. Overall design: single cell RNA sequencing comparing myeloid cells from tumor-involved and uninvolved tissues. GSE219197 pubmed 36795805