The severe developmental defect of NK cells in CXCR4 conditionally deficient mice. (A-D) Flow cytometric analysis of the numbers of Lin⁻ (TER119⁻Mac-1⁻Gr-1⁻ CD3⁻CD4⁻CD8⁻) NK1.1⁻DX5⁻CD122⁺ NKPs, CD3⁻NK1.1⁺DX5⁻ iNKs, and Mac-1⁻ and Mac-1⁺ subsets of CD3⁻NK1.1⁺DX5⁺ mNKs in the bone marrow (2 femurs and tibiae) (A), and CD3⁻NK1.1⁺DX5⁺ mNKs in spleen, lung, and peripheral blood (B) from untreated MxCre/CXCR4^f/wt, pIpC-treated MxCre/CXCR4^f/wt, or MxCre/CXCR4^f/null mice; n = 4. (C) Immunofluorescent profiles of NK cells. Gated CD3⁻NK1.1⁺DX5⁺ are analyzed for the expression of Mac-1 and CD27. (D) Flow cytometric analysis of the frequencies of bone marrow CD3⁻NK1.1⁺ NK cells expressing KLRG1, Ly49A, C/I, D, G2, or CD94/NKG2; n = 4. (E,G) Quantitative RT-PCR analysis of mRNA expression of Perforin in CD3⁻NK1.1⁺DX5⁺ mNKs in the bone marrow and spleen (E) and E4BP4 in mNKs in the bone marrow (G) from pIpC-treated MxCre/CXCR4^f/wt or MxCre/CXCR4^f/null mice. Results are expressed as fold difference compared with the levels found in samples from MxCre/CXCR4^f/wt mice (GAPDH normalization); n = 3. (F) BrdU was administered over a 3-day period. The frequencies of CD3⁻NK1.1⁺DX5⁻ iNKs incorporated BrdU over this period were analyzed by flow cytometry; n = 3. *P < .05. **P < .01. ***P < .001.