PDCD1 and mature T-cell and NK-cell non-Hodgkin lymphoma: GEP showed that genes associated with innate immune response were abnormally expressed in PD‐1 (+) cells of PTCL patients compared with healthy subjects, meanwhile the expression of CTLA‐4 was significantly higher in PD‐1 (+) cells than that of PD‐1 (−) cells.