The analysis results of the relationship between flow cytometry results and clinical characteristics showed that the level of PD-1 in CD4+ T cells from peripheral blood was higher in cHL patients with stage III-IV (P = .0178), B symptoms (P = .0398), higher LDH (P = .0056), higher international prognostic index (IPI) score (P = .0349), and relapsed in later stages (P = .0306) (Fig. 1B). The gene discussed is PDCD1; the disease is classic Hodgkin lymphoma.