FOXP3 and chronic obstructive pulmonary disease: However, the difference in Foxp3 expression among different compartments was already addressed in a study by Sales et al. (2017), which demonstrated a decrease in Foxp3+ cells in the small airways of patients with COPD compared to the control group, whereas evaluation of lymphoid tissue showed an increase in Foxp3+ cells in the non-obstructive smoker and COPD groups.