CXCR4 and paroxysmal nocturnal hemoglobinuria: Although we confirmed that the CXCR4 expression on GPI(−) HSPCs of PNH patients was much lower than that on GPI(+) HSPCs of HIs, the failed lipid raft formation cannot explain the comparable expression levels of CXCR4 between GPI(−) B and GPI(+) B cells of the same patients.