There was no change in the percentage of large (proximal) airway (LA) brushing CD8+ or CD4+ intraepithelial lymphocytes between COPD compared with controls (CD8+ T cells: COPD 74% (56–88), control 67% (31–88) (median (range)); (CD4+ T cells: COPD 22% (15–42) control 31% (15–65) (median (range)). Here, CD4 is linked to chronic obstructive pulmonary disease.