2011). We administered rituximab (1,000 mg; day 0 and 14) to seven BP subjects with recalcitrant disease to determine the safety, efficacy, and mechanisms related to rituximab treatment response and relapse. Seven BP subjects with persistent disease activity despite X17. 5mg per day prednisone were studied (five female subjects; two male subjects; mean disease duration 3.2 years)(Supplementary Table online), in accordance with the Declaration of Helsinki Principles and the Institutional Review Board of Duke University. Subjects were followed up for 12 months. Disease flares were defined as the development of any disease activity necessitating an increased dose of prednisone. All subjects tolerated the infusions well with no drug-related serious adverse events. All subjects experienced a cessation of new skin lesions and a prednisone dose of 25% of starting dose or 10mg at 6 months. Total disease activity significantly improved at 6, 9, and 12 months compared with baseline (P¼0. 0156, Wilcoxon test). Two subjects experienced a flare of their disease activity at months 7 and 11.5. Subjects were evaluated by ELISA for IgG anti-BP180 and anti-BP230 autoantibodies (MBL, Woburn, MA) and IgE anti-BP180 using the NC16A domain of BP180 as described (Messingham et al., 2009). IgG anti-varicella zoster antibody levels (Trinity Biotech, Jamestown, NY) and serum B-cell activating factor (BAFF) levels (R&D Systems, Minneapolis, MN) were determined by ELISA. Analysis of peripheral blood B cells was conducted by flow cytometry as described