WAS patients display more ICOS expression in CD4⁺ CXCR5⁺ T cells. (A) Flow cytometric analysis of ICOS⁺ cells in whole blood and stimulated PBMCs from WAS patients and HCs. (B) Percentage of ICOS⁺ cells within CD4⁺CXCR5⁺ T cells in WAS patients (n = 18; P1-P18) and HCs (n = 18). (C) Percentage of ICOS⁺ cells within CD4⁺CXCR5⁺ T cells after stimulation with PHA for 3 days in WAS patients (n = 8; P1-P8) and HCs (n = 7). (D) Representative images of ICOS staining in Tfh cells from HCs and WAS patients. Scale bar, 2.5 μm. (E) MFI of ICOS on the plasma membrane and cytoplasm of Tfh cells from HCs and WAS patients.