Rituximab leads to rapid and sustained elimination of circulating CD20⁺B and T lymphocytes despite ongoing TPEx in patients with iTTP. (A) Total circulating lymphocytes in patients with iTTP decrease after rituximab administration but there remains a variable response between the first and second dose of rituximab (days 1-7) and during continued TPEx. (B) Circulating CD20⁺ B lymphocytes vary in number in each patient. Rituximab removes nearly all circulating CD20⁺ B lymphocytes in each patient even after TPEx 24 hours later. The CD20⁺ B cells remain absent a week later at the time for the next rituximab treatment. (C) CD20⁺ is expressed on most circulating B lymphocytes in each patient at diagnosis. Rituximab quickly removes circulating CD20⁺ B lymphocytes within 24 hours. Recovery of CD20⁺ B lymphocytes by day 7 is patient-dependent, with patient 3 (P3) having the most circulating cells. (D) Specific circulating T lymphocytes in iTTP express CD20 and levels depend on the patient. Rituximab effectively depletes CD20⁺ T cells, which last 1 week after administration. (E) CD4-to-CD8 ratios are decreased between day 0 and day 1 in all patients, suggesting preferential depletion of CD4⁺ T cells. (F) Flow cytometry plots demonstrate that CD20⁺ B cells were eliminated (boxed regions) in each patient after rituximab treatment between day 0 and 1. The number of CD20⁺ T cells dropped dramatically (although to variable extent in different patients) within 24 hours after rituximab treatment (arrows). Bars and lines represent mean percentages plus standard deviation from N = 3 patients.