CD4 and neoplasm: In addition to killing tumor cells, activated phototoxic agents remodel the tumor microenvironment and convert the immunogenic “cold” environment to a “hot” one, including activation of tumoricidal macrophages, dendritic cell (DC) maturation, infiltration of CD4+ and CD8 + T cells, and suppression of myeloid-derived suppressor cells (MDSC)240,241.