WASP positively regulates the CD19 transcription. HCs and WAS naive and memory B cells were distinguished by IgD and CD27 staining. Surface staining of CD19 (A) and FcγRIIB (B) and intracellular staining of Btk (C) in naive or memory B cells. The quantification of MFI of CD19 and CD81 in naive or memory B cells from HCs or WAS patients (P4-P13) (D). HCs and WAS naive and memory B cells were sorted by CD19, CD27, and IgD staining, and sorted cells were lysed for mRNA extraction. Real-time polymerase chain reaction was performed by using primers specific for cd19, cd32, and btk (E). Enriched B cells from HCs (F) and WAS (P3-P15) (G) PBMCs were stimulated with soluble antigens for varying lengths of time, fixed, and stained with anti-CD69 and CD80 antibody for flow cytometry. The quantification of MFI of CD69 (H) and CD80 (I) in naive or memory B cells from HCs or WAS patients. 293 cells in 24-well plates were transfected with 0.45 μg pGL3-CD19, 0.45 μg pcDNA3.1or pcDNA3.1-WASP, and 0.045 μg pRL-TKB (internal control) for 24 hours following with luciferase reporter assay, pGL3-promoter, and pGL3-basic used as positive and negative controls (J).