The observation that the lung phenotype of TLR2−/− or TLR4−/− mice did not differ from C57BL/6 wildtype (WT) mice revealed that the single knockout mice (TLR2−/− or TLR4−/−) have similar sensitivity to WTI-induced alveolitis and fibrosis as WT mice. Here, TLR2 is linked to hypersensitivity pneumonitis.