TGFB1 and systemic lupus erythematosus: Moreover, it was found that mRNA levels of TLR9 were correlated with TGF-β1 (p < 0.0001, r = 0.52; Fig. 2g) and PDGF-B (p < 0.0001, r = 0.45; Fig. 2h) in SLE patients.