PD-L1+ macrophages suppress T cell-mediated anticancer immunity.

Recently, we showed that an autologous DC-based vaccine induces an increase in immunosuppressive PD-L1+ tumor-associated macrophages (TAM) both in the tumor and the tumor draining lymph nodes, thereby blunting the efficacy of therapeutic immunization. Only the combination of the DC vaccine with anti-PD-L1 immune checkpoint inhibition, but not the use of antibodies targeting PD-1 alone, was able to set off CD8+ cytotoxic T lymphocyte (CTL)-mediated tumor suppression in mice. In sum, we delineated a PD-L1 checkpoint blockade-based strategy to avoid TAM-induced T cell exhaustion during DC vaccine therapy.