CD27 and chronic obstructive pulmonary disease: Compared to lung CD4+ T cells of smokers with preserved lung function (n = 7), those of subjects with COPD (n = 15), showed a significant decrease in the percentage of lung CD4+ T cells that were double-negative for CD62L and CD27 (Fig. 2C), which have conventionally been thought to be the active TEM phenotype responsible for most cytokine secretion.