Latent TGF-beta1 associated with SP-A: Possible novel mechanism to regulate TGF-beta1 mediated inflammation and fibrosis in the lung

Surfactant protein A (SP-A) and active transforming growth factor beta (TGF-beta) 1 have been shown to modulate the functions of various immune cells in the lung. TGF-beta1 is released by cells as latent, biologically inactive complexes. After an activation step TGF-beta1 signaling from the cell membrane to the nucleus is mediated through Smad2/3 proteins. The signaling pathway of SP-A is however unknown. The aim of the present study was to elucidate if the Smad signaling pathway plays also a role in mediating the immune modulation of SP-A. Primary human CD4+ T lymphocytes were transfected with a Smad3 signaling…