The findings suggest a close association between HMGB1 and the immune checkpoint PD-1/PD-L1, indicating that serum HMGB1 may exert inhibitory effects on T cell proliferation and activation by modulating the expression of CD28 and PD-1 on T cell surfaces, which plays a pivotal role in tumor immune evasion. The gene discussed is PDCD1; the disease is neoplasm.