Non-small cell lung cancer (NSCLC) represents one of the most common and aggressive cancers worldwide. The PD-1/PD-L1 interaction plays important roles in cancer immunology, and expression of PD-L1 has been discovered in NSCLC tumor cells. Since follicular helper T (Tfh) cells have characteristic high PD-1 expression, we therefore investigated the inflammatory status of Tfh in NSCLC. CD4(+) CXCR5(+) T cell population was examined to define Tfh cells. Data showed that frequency of Tfh cells in peripheral blood was significantly lower in NSCLC patients than in healthy controls. In both primary and metastatic tumors, infiltration of Tfh cells was observed, suggesting that they participated in the antitumor immunity of NSCLC patients. Compared to other T cell subsets, the Tfh cells from the peripheral blood and the resected tumors of NSCLC patients presented elevated apoptosis and reduced proliferation capacity. The Tfh cells from NSCLC patients were also less effective at downregulating IgD and upregulating CD27 expression in naive B cells, and induced less IgM, IgG and IgA secretion, than those from healthy controls. We then found that the survival time from the date of surgery was positively correlated with the frequency of tumor-infiltrating Tfh cells in NSCLC subjects. Overall, the results from this study demonstrated that the Tfh cells were likely involved in the antitumor immunity and were associated with better clinical outcomes, but suffered strong immunosuppression in NSCLC. Enhancing the Tfh cell activity therefore represents a potential therapeutic strategy in NSCLC. (C) 2016 Elsevier B.V. All rights reserved.