Other studies have shown that the level of PD-1 in peripheral blood T lymphocytes is positively correlated with the staging and clinical progression of cervical cancer[14] and gastric cancer.[15] Similarly, this study also found that PD-1 levels on CD4+ T cells from peripheral blood was higher in cHL patients with stage III-IV, B symptoms, higher IPI score, and higher LDH concentration. Here, CD4 is linked to classic Hodgkin lymphoma.