CD11b^hiCD27^low NK cells are absent in Txb21^−/− mice but can be rescued in a Txb21^+/+ environment. (A) Expression of CD11b and CD27 in spleen NKp46⁺CD3⁻ NK cells of Txb21^+/+ (top panel) and Txb21^−/− (bottom panel) C57BL/6 mice. (B) Frequency (mean ± SD) of CD11b^hiCD27^low NK cells of 6 mice per genotype in the indicated organs. (C) Frequency (mean ± SD) of CD11b^hiCD27^low NK cell of Txb21^+/+ and Txb21^−/− C57BL/6 mice prepared from spleen of 5 mice per genotype at the ages indicated. (D) Txb21^−/− spleen cells were labeled with CFSE and injected intravenously into Txb21^−/− or Txb21^+/+ hosts. Shown is the expression of CD11b and CD27 in the transferred CFSE⁺ (top panels) and host CFSE⁻ (bottom panels) NKp46⁺CD3⁻ NK cells in Txb21^−/− (left panels) and Txb21^+/+ (right panels) hosts. (E) Frequency of CFSE⁺ CD11b^hiCD27^low NK cells in 5 Txb21^−/− and 5 Txb21^+/+ mice. (F) Six Txb21^+/+ and 5 Txb21^−/− CD45.1 host mice were irradiated and transferred with Txb21^−/− CD45.2 BM cells. Shown is the frequency of donor CD45.2 CD11b^hiCD27^low NK cells. (E-F) Bars represent the means within the groups.