The mucosal immune system has been efficiently repopulated with donor-derived CD4⁺ T cells. (A) Immunohistochemical quantification of CD4⁺ T cells in colon tissue of the CCR5Δ32/Δ32 SCT patient, SCT control patients (27 ± 9 months after transplantation), and healthy control patients. The horizontal lines denote the median values of each group. (B) Genomic DNA was extracted from mucosal CD4⁺ T cells and subjected to CCR5-specific PCR spanning the Δ32 region.