The infiltration of tumor tissue by pDCs has been associated with worse overall survival, a shorter time to relapse, and increased tumor invasion in both HCC [386, 387] and iCCA [388], as well as with ICOS-ICOSL-mediated activation of a CD4+ FoxP3− IL-13− IL-10+ Tr1 regulatory cell subset that can suppress the antitumor response [389]. Here, ICOS is linked to hepatocellular carcinoma.