Therapeutic intervention with the monoclonal anti-HMGB1 antibody ameliorates clinical progression of collagen-induced arthritis. Mice were treated for 7 d with monoclonal anti-HMGB1 antibody 2G7, initiated when the animal reached a clinical arthritis score of ≥2. Disease development was significantly ameliorated in 2G7-treated mice (n = 12), compared with mice treated with irrelevant antibody (n = 7). Values are median clinical score, and error bars represents interquartile range. Statistical analysis of clinical arthritis score is based on calculated area under the curve values for individual animals in each group, and the differences between animals in the two studied groups were analyzed by two-tailed, nonparametric Mann-Whitney test.