The molecular mechanism of this potential synergistic effect has not yet been fully explained; however, our C57BL/6 mouse lung cancer model study demonstrated an increase in the expression of PD-L1 and CD8+ T lymphocytes in the immune microenvironment with combination therapy of anti-PD-1 antibody plus chemotherapy, especially in the group of half-dose chemotherapy and anti-PD-1 antibody (data not shown), which may be a factor. The gene discussed is PDCD1; the disease is lung carcinoma.