Surface expression of HIV-1 coreceptors on CD4⁺ cells in various organs of mice 4 months after transplantation. A representative FACS profile of human CXCR4 and CCR5 on CD4⁺ cells shows the existence of CXCR4⁺CD4⁺ and CCR5⁺CD4⁺ cells in blood (A), spleen (B), and BM (D), but no CCR5⁺CD4⁺ cells in the thymus (C). BM results show that many CD4⁺ cells are neither CD3⁺ T cells nor CD14⁺ monocytes. A gate was set on the human CD45⁺ population.