Results: Our studies provide evidence that photothermal effects kill tumor cells mainly via inducing apoptosis, which can significantly improve antitumor immunity when IDO was down-regulated in TME through significant increases of localized CD8+ and CD4+ lymphocytes in tumor tissue, the downregulation of CD8+ and CD4+ lymphocyte apoptosis, and the upregulation of antitumor cytokines, TNF-α and IFN-γ. The gene discussed is CD4; the disease is neoplasm.