TLR9 and systemic lupus erythematosus: However, when we analyzed the correlations between TLR9 expression and IL-6 and ds-DNA antibody levels in SLE patients, the results showed that TLR9 overexpression was positively correlated to IL-6 or ds-DNA antibody level during SLE development (for IL-6, R2 = 0.768, for ds-DNA, R2 = 0.730, Figures 2(c) and 2(d)).