Gzmb^Cre;Rosa26^{ACTB-tdTomato, -EGFP/+} mice have a low frequency of GFP⁺ mature NK cells.

(A) Representative FACS histograms showing the gating strategy for mNK cells in Gzmb^Cre;Rosa26^{ACTB-tdTomato, -EGFP/+} mice. Lymphoid cells were gated by FSC and SSC (left panel) and then Lineage negative, PI- cells (center plot) were selected and examined for expression of NK1.1 and CD122. (B) The frequency of mNK cells expressing GFP in a typical Gzmb^Cre;Rosa26^{ACTB-tdTomato, -EGFP/+} mouse bone marrow (BM), spleen, lymph node (LN) and liver. The frequency of GFP⁺ cells is indicated. (C) Scatter plots showing the frequency of YFP⁺ mNK cells in the bone marrow of multiple Gzmb^Cre;Rosa26^{ACTB-tdTomato, -EGFP/+} mice at different ages. Each circle represents one mouse. (D) The average number of GFP⁺ mNK cells is shown for each of the indicated tissues in mice between 6 and 12 weeks of age. Error bars = standard deviation. n > 7 for each tissue. The difference in average GFP⁺ mNK cell number between different tissues was not statistically significant.