Distribution of human NK cells in reconstituted NSG mice. Frequency within human CD45 positive cells and total number of CD3⁻NKp46⁺ human NK cells in spleen, blood, lung, liver, and bone marrow (BM) of NSG mice reconstituted with human immune system components 3 months after transfer of CD34⁺ hematopoietic progenitor cells. Representative flow cytometric staining from 1 mouse (A) and composite data from 7 mice (B-C) are shown. Numbers in plots represent frequencies within gates.