Given that PD-1 expression was higher in tumor infiltrating DNT cells than those in adjacent or normal lung tissues (Fig. 3a), and lung cancer cell lines express different levels of PD-L1 (Additional file 2: Figure S3A), we determined if co-culture of DNT cells with lung cancer cells was sufficient to induce PD-1 expression. The gene discussed is PDCD1; the disease is neoplasm.