HMGB1 in human IPAH. (A) Localization of HMGB1 in lung sections of patients with and without IPAH by immunohistochemistry (brown = HMGB1, blue = hematoxylin, scale bar = 50 µm). (B) Circulating HMGB1 was measured in serum from IPAH patients (n = 21) or healthy controls (n = 15). Open circles show the levels of individual patients. The line and error bars show the mean and 95% confidence intervals. (C) Correlation of mean pulmonary artery pressure (mPAP) with circulating HMGB1 levels in IPAH patients (n = 16 patients). The r represents the Pearson correlation coefficient. Dashed lines represent the 95% confidence intervals.