TGFB1 and pulmonary fibrosis: Interestingly, there was no change in TGF-β production by purified T cells, and PFD had no effect on the suppressive properties of naturally occurring regulatory T cells [25] In addition, the antifibrotic effect of PFD may be mediated through inhibition of heat shock protein 47, a collagen-specific molecular chaperone, with a resultant reduction in collagen synthesis in lung fibrosis [26].