TLR4 and pulmonary fibrosis: Interestingly, studies on the development of post-radiation pulmonary fibrosis in mice with global deficiency of TLR2 and TLR4, as well as with the knockout of MyD88 (Innate Immune Signal Transduction Adaptor) showed that these mice developed more severe pulmonary fibrosis compared to wild-type mice (60, 64, 65).