F2RL1 and pulmonary fibrosis: Therefore, in concurrence with the previously documented roles of ARG-1 in pulmonary fibrosis, our data showing reduced ARG-1 expression in the lungs of Par2 KO mice not only further strengthens the notion that ARG-1 expression is a contributing factor to reduced airway collagen deposition but also introduces potential interplay between PAR2 and ARG-1.