Increased frequency of Ly49G2^high NK cells in congenic and syngeneic HSCT. Lethally irradiated B6 (H-2^b, CD45.2) mice were transplanted with 5 × 10⁶ Ly5.2 congenic (H-2^b, CD45.1) BMCs depleted of NK and T cells. Splenocytes of recipients were stained for CD45.1, NK1.1, CD3, Ly49C/I, Ly49A, and Ly49G2 at day 14 after congenic HSCT and compared with untreated control mice. Gated CD45.1⁺NK1.1⁺CD3⁻ are shown. (A) Frequencies of NK cells positive for Ly49G2, Ly49CI, and Ly49A. (B) Intensity levels of Ly49G2 expression as determined by MFI on control (tinted gray) and transplanted (solid dark line) mice. (C) Frequencies of NK-cell subsets. *P < .001. (D) NK cells (CD45.1⁺CD122⁺CD3⁻ CD19⁻) were sorted from spleen cells of control or transplanted B6 (H-2^b) mice (day 14) and used in a 4-hour killing assay against YAC-1 to assess cytotoxicity. Lethally irradiated B10 (H-2^b) and B10.D2 (H2^d) mice were transplanted with 5 × 10⁶ syngeneic BMCs depleted of NK and T cells. Splenocytes of recipients were stained for CD45, NK1.1, CD3, Ly49C/I, and Ly49G2 at day 14 after syngeneic HSCT and compared with untreated control mice. Gated CD45⁺NK1.1⁺CD3⁻ cells are shown. (E) Frequencies of NK cells positive for Ly49G2 and Ly49C/I. (F) Intensity levels of Ly49G2 expression as determined by MFI on control (tinted gray) and transplanted (solid dark line) mice. Distribution of NK-cell subsets in B10 (G) and B10.D2 (H) are shown. *P < .001; **P < .01. The numbers represent the percentages of cells or MFI values. Data are representative of 3 experiments using 3-4 mice per group in each experiment (means ± SEM).