TLR4 and chronic obstructive pulmonary disease: Previously, we found increased TLR2 expression in the peripheral blood of COPD patients [21], while in this study, end-stage COPD patients had increased mRNA level of TLR4 before LT, but TLR4 was down-regulated in lung recipients and its relative expression level was similar to that one in healthy control group (Supplementary Table 3) [21].