Generation and characterization of Ncr1-iCreTg mice. (A) Schematic illustration of the modified Ncr1 BAC. iCre cDNA was inserted by homologous recombination into the exon containing the translation initiation codon of a BAC harboring the mouse Ncr1 gene. (B) Efficiency of Cre-mediated eGFP expression verified via flow cytometry of Ncr1-iCreTg eGFP-LSLTg double-transgenic mice and littermate controls. Excision of a stop cassette flanked by loxP sites leads to eGFP expression that can be analyzed by flow cytometry. Numbers adjacent to outlined areas indicate the percentage of NK cells (TCRβ⁻NKp46⁺) of various lymphoid organs. Histograms show the percentage of eGFP expression of gated NK cells. (C-F) Flow cytometry of Ncr1-iCreTg eGFP-LSLTg double-transgenic mice and their littermate controls showing the absence of eGFP expression in hematopoietic cell lineages other than NK cells. Dot plots indicate the percentages of (C) gated CD3⁺ CD4⁺CD8⁺ cells, (D) gated CD3⁻ NK1.1⁺CD1d tetra⁺ cells, (E) gated CD3⁺ TCRγδ⁺ TCRβ⁺ cells, and (F) B220⁺CD19⁺ cells. Histograms show the percentage of eGFP expression. (G) Almost all NK cells express eGFP. Approximately 99% of gated TCRβ ⁻eGFP⁺ cells are NK cells (NK1.1⁺NKp46⁺; n ≥ 4 per genotype). Data are representative of at least 3 independent experiments. BM, bone marrow; LN, lymph nodes.