FACS analysis of BM cells from α4-deficient or control mice. (A) Note the absence of α4 expression and the left shift in β1 integrin expression of BM cells from α4^Δ/Δ mice compared to controls (4 left panels). Solid lines represent isotype control antibody. (ii) Proportions of Lineage^-/Sca-1⁺/kit⁺ (LSK) cells containing an enriched population of stem cells. Gated Lineage^-/kit⁺ cells (top left) were tested for Sca-1 positivity (ii). No differences are seen between the α4^Δ/Δ (neonatally ablated and tested at 14 weeks) and control mice (14 weeks old), suggesting normal representation of LSK cells in α4-deficient mice. Furthermore, kit⁺ cells did not express α integrin (panel B). In panel C, BM cells were labeled with anti-CD150 PE and anti-CD48 FITC. Among more than 2 × 10⁵ cells analyzed, the proportion of CD150⁺ CD48^- cells were 0.014% and 0.02% (2 experiments) in control and 0.18% and 0.03% in neonatally ablated α4^Δ/Δ animals of the same age (4-5 months). No α4⁺ cells were seen among CD150⁺CD48^- cells from α4^Δ/Δ BM (data not shown). The proportion of CD150⁺CD48⁺ was 4.09% in controls and 6.62% in α4^Δ/Δ. It is of interest that all kit⁺ cells were CD48⁺ in both sets of animals.