To establish a negative regulation of TGFβ1-induced ECM protein production by SEMA3B, we measured the protein levels of COL1, ELN, FN1, and αSMA in cell lysates of IPF fibroblasts treated with TGFβ1 in the presence or absence of SEMA3B. Here, TGFB1 is linked to idiopathic pulmonary fibrosis.