Airway bacteria have long been thought to contribute to COPD pathology50 and more recently have been implicated as a driver of TLS formation.23,51 While pIgR−/− mice, like patients with COPD, do not appear to have bacterial overgrowth in the lungs,14,52 our data suggest that endogenous bacteria are more frequently localized within the epithelial layer, where they are capable of activating inflammatory signaling cascades. Here, PIGR is linked to chronic obstructive pulmonary disease.