PDCD1 and mature T-cell and NK-cell non-Hodgkin lymphoma: Our results showed that genes associated with innate immune response and IFN‐γ pathway were abnormally expressed in PD‐1 (+) cells of PTCL patients compared with the healthy controls, meanwhile PD‐1 (+) cells demonstrated a markedly raised CTLA‐4 expression, an important inhibitory molecule for lymphocytes, in contrast to PD‐1 (−) cells in PTCL patients.