Toll-like receptor 9 is correlated to disease activity in Chinese systemic lupus erythematosus population

Methods mRNA level of TLR9 and interferon （IFN） regulatory factor 5 （IRF5） in peripheral blood mononuclear cells （PBMCs） were determined by real-time polymerase chain reaction （PCR）. IFN-a expression was measured in the serum of the SLE patients by enzyme-linked immunosorbent assay （ELISA）. Results TLR9 expression was significantly higher in SLE patients than that in health controls （P=0.011）. SLE patients with positive anti-dsDNA antibody had significantly higher expression of TLR9 than that with negative anti-dsDNA antibody （P=0.001）. TLR9 expression was positively correlated with fever （P=0.017）, alopecia （P=0.046）, safety of estrogens in lupus erythematosus national assessment SLE disease activity index （SELENA-SLEDAI） score （rs=0.385, P=0.003）, and the level of IRF5 （rs=0.35, P=0.027） and IFN-a （rs=0.627, P=0.001） in SLE patients. Conclusion TLR9 is associated with SLE disease activity and might be involved in the IFN-a pathway of SLE.