TLR4 and pulmonary emphysema: Furthermore, these observations that the specific reduction of Tlr4, but not Tlr2, gene expression in the mouse correlated with the onset of emphysema were also validated in human disease, whereby among members of the TLR family, only TLR4 gene expression was significantly suppressed in human lung tissue from individuals with emphysema versus emphysema-free controls (Figure 2).