Serologic responses to rituximab. (A) Normalized antibody titers. The 2 left panels demonstrate the decreasing antibody titers against 2 H-Y antigens, DBY and UTY, in 4 male patients with female donors. Each subject has 5 measurements, including baseline (week 0) after 1 course of rituximab (week 9), after a second course of rituximab (week 17), 6 months after rituximab (week 27), and 1 year after rituximab (week 52). The 2 right panels demonstrate the stable or increasing titers against 2 non–H-Y antigens, EBV and tetanus. The dashed horizontal line represents the baseline level. (B) Box and whisker plot of EBV and tetanus titers in 12 patients. The boxes represent the 25th and 75th percentiles of the antibody titers measured. The whiskers represent the 5th and 95th percentiles of the measured values. The horizontal line within each box is the median antibody titer measured. All comparisons are P = NS.