Although these mice appeared healthy at birth and demonstrated no histopathologic changes in the lungs compared with wild-type (WT) littermate controls at 2 months of age, pIgR−/− mice developed COPD-like changes with fibrotic small airway remodelling and emphysematous destruction of the lung parenchyma by 6 months of age, which continued to worsen in 12-month-old mice (Fig. 1c–f). Here, PIGR is linked to chronic obstructive pulmonary disease.