CD4 and non-small cell lung carcinoma: It has been shown that PD‐1 is mainly expressed on CD8+ rather than CD4+ T cells,33, 34 and low PD‐1 expression in CD8+ T cells confers a survival advantage in NSCLC.28 In a study of mouse‐transplanted colon cancer, macrophages, apart from lymphocytes, expressed high level of PD‐1 to inhibit phagocytosis and tumor immunity.35 Our study underlines the need to further identify which immune cell subpopulation expresses PD‐1/PD‐L1 and its' predominant spatial distribution, and whether and to what extent it affects immune activation or inhibition.