Also, smoking history (pack-years) in smokers with normal lung function and smokers with COPD, as well as in ex-smokers with COPD, correlated positively with MUC5AC expression in goblet cells (Figure 3C) and negatively with the immunohistochemical MUC5B expression in goblet cells (Figure 3D). Here, MUC5B is linked to chronic obstructive pulmonary disease.