Normal cell numbers of NK cells in CXCR4-deficient fetal thymus. Flow cytometric analysis of NKPs and NK cells in CXCR4^null/null fetal thymus. (A) Fluorescence staining profile of Lin⁻ (TER119⁻Mac-1⁻Gr-1⁻B220⁻CD3⁻CD4⁻CD8⁻) NK1.1⁻CD25⁻ cells (left) and the numbers of Lin⁻NK1.1⁻CD44⁺CD25⁻CD122⁺ NKPs (right) in E15.5 fetal thymus. (B) The numbers of CD3⁻NK1.1⁺DX5⁺ mNKs in E17.5 fetal thymus; n = 4.