TLR4 expression was increased in the epithelium of distal airways (figure 1 A and figure 2 A) in S, in s-COPD and in ex-s-COPD when compared to C. In central airways TLR4 expression was increased in S and s-COPD when compared to C and the TLR4 expression was significantly higher in S than in s-COPD (figure 1 B and figure 2 B). Here, TLR4 is linked to chronic obstructive pulmonary disease.