Effect of RTX on splenic lymphocytes and CD8⁺localization. (A) Splenic lymphocyte subsets were compared among controls (black circles, n = 9), RTX-untreated ITP patients (black squares, n = 11), and RTX-nonresponder ITP patients (black triangles, n = 12). Data representing the percentage of B cells (CD19⁺), T cells (CD3⁺), and the cytotoxic/helper T-cell ratio (CD8⁺/CD4⁺) are summarized in dot plots. The horizontal bar represents the median with the interquartile range. P values were derived by Mann-Whitney U test. **P < .01; ***P < .001. NS, nonsignificant. (B) On immunohistochemistry analyses, CD8⁺ T cells were preferentially located in the red pulp (left panel, anti-CD8, DAB, magnification ×400) and also in periarteriolar lymphoid sheaths (PALS) (left panel, within the dashed circle). Platelets were found in the red pulp (black arrows, right panel, anti-CD61, Ultra-Red, magnification ×800) and into macrophages (white arrows). Representative immunohistochemistry of 1 RTX-nonresponder ITP patient.