TLR9 and systemic lupus erythematosus: Studies have shown that the levels of TLR9, TGF-β1, and PDGF-B in peripheral blood of SLE patients are higher than those of normal controls, and patients with significantly increased TLR9 mRNA at the time of initial diagnosis may experience a poor prognosis in the short term, suggesting that TLR9 may be associated with the prognosis of SLE [23].