Serum HMGB1 levels in different World Health Organization (WHO) classes. Serum levels at baseline and follow-up in lupus nephritis patients with WHO III (n = 9) versus IV (n = 11) are shown. After induction therapy, serum levels of HMGB1 were significantly decreased in patients with WHO class IV. However, HMGB1 levels remained unchanged in patients with WHO class III. Data are expressed as means, and vertical bars denote 95% confidence intervals. HMGB1, high-mobility group box 1 protein.