CXCR4 surface expression on peripheral and mucosal CD4⁺ T cells is not impaired in the CCR5Δ32/Δ32 SCT patient. CD4⁺ T cells in (A) fresh whole blood, MMC (5.5 months after transplantation), or (B) ex vivo PHA/IL-2–activated PBMCs were analyzed for the frequency of CXCR4 surface-expressing cells and the CXCR4 expression density. CXCR4 expression density on CD4⁺ T cells was evaluated as the MFI of CXCR4 expression divided by the MFI value obtained with the corresponding isotype control and is expressed as the MFI ratio.