TLR3 and fibrosis: However, the correlation of TLR3 polymorphism with persistent disease in sarcoidosis (some of which with fibrosis) and highly progressive IPF suggests that it is possible that the TLR3 signalling pathway anomalies are involved in susceptibility to fibrotic pulmonary sarcoidosis, either via loss of function in innate immune cells like macrophages or reduced apoptosis in lung fibroblasts [38].