Poor lymphoid reconstitution in transplant recipients of Pbx1^−/−Rag1^−/− bone marrow cells. (A) FACS analysis using NK and T cell-specific fluorochrome-conjugated antibodies was performed on cells from the peripheral blood of chimeric and control mice.²⁶  Very few Ly9.1⁺NK1.1⁺ cells were detected in the Pbx1^−/−Rag1^−/− adult chimeric mice. All NK1.1⁺ cells in Pbx1^−/−Rag1^−/− chimeric mice were TCRαβ⁺ (NKT cells) in contrast to Pbx1^+/+Rag1^−/− mice. Analyses of Rag1^−/− and 129 mice are shown for comparison. (B)Equal numbers of donor-derived (Ly9.1⁺) Pbx1^−/− or Pbx1^+/+ cells were FACS purified from Rag1^−/− blastocyst-complemented mice and transplanted into lethally irradiated C57BL/6 recipients along with 2 × 10⁶Rag1^−/− bone marrow cells. No donor-derived B cells were detected in the peripheral blood of recipients receiving Pbx1^−/−Rag1^−/− bone marrow in contrast to recipients of control Pbx1^+/+Rag1^−/− bone marrow. Reconstitution of TCRαβ cells was present, but poor, in recipients receiving Pbx1^−/−Rag1^−/− bone marrow.