The observed difference in IL-35 titers (between COPD sufferers and asthmatic patients) was attributed to the disparate cellular sources that promote each airway pathology namely; CD4+ T cells in asthma and CD8+ T cells in COPD.Foxp3+ Tregs cells are a principal source of IL-35, hence the higher expression levels in asthma. Here, FOXP3 is linked to asthma.