IL-10R expression is low or absent on the malignant T cells. (A) Representative flow cytometric analysis of IL-10 receptor (IL-10R) expression on the benign T-cell line, MF1850, and the malignant T-cell line, SeAx. (B) Representative flow cytometric analysis of IL-10R expression on benign (CD4⁺CD26⁺) and malignant (CD4⁺CD26⁻) T cells in PBMCs from an SS patient. (C) Graph showing the average percentage of IL-10R–positive benign (CD4⁺CD26⁺) and malignant (CD4⁺CD26⁻) T cells in PBMCs isolated from 5 SS patients. Bars represent SEM. FSC-H, forward scatter height; SSC-A, side scatter area.