Figure 4From: Variability in the precursor proteins of collagen I and III in different stages of COPD Immunohistochemical staining for precursor protein of collagen III in small airways of a non-smoker (A), a smoker (B), a patient with stage I COPD (C) and a patient with stage IV COPD (D). showing increased expression of precursor protein of collagen III in small airways of smokers and stage I-II COPD, and decreased expression in stage IV COPD.Back to article page