PDCD1 and lymphoma: The proportions of PD-1+ cells in CD4+ lymphocyte populations obtained from PBMCs and LNCs were significantly higher in the lymphoma group (PBMCs, mean ± standard deviation: 46.67% ± 18.52%; LNCs, 61.29% ± 16.99%) than in the control group (PBMCs, 30.79% ± 7.18%, P = 0.011, Fig 1A; LNCs, 29.48% ± 7.90%, P < 0.001, Fig 1C).