A study found, the level of pIgR in the bronchial epithelium of severe COPD patients was lower than that in the control group, and the pIgR and IgA transport in the bronchial epithelial cell of severe COPD patients was reduced [31], This may be related to the chronic accumulation of CD8+ T lymphocytes in the small airways. Here, CD8A is linked to chronic obstructive pulmonary disease.