PIGR and chronic obstructive pulmonary disease: Since elevated microbes can drive the COPD-like phenotype in pIgR deficient mice (Richmond et al., 2016) and downregulation of pIgR is observed in COPD patients (Gohy et al., 2014), reduced pIgR expression could be an underlying mechanism of the increased incidence of COPD in HIV/AIDS patients (Morris et al., 2011).