Redundancy between Shh and Ihh in early thymocyte development. (A,B) Flow cytometry of E13.5 Ihh+/+, Ihh+/−, Ihh−/−, and Ihh−/−Shh+/− thymi. (A) Dot plot of anti-CD45.2 staining versus FSC, showing the gate used for analysis of lymphocyte precursors. (B) CD44 and CD25 expression of thymocytes, gated on CD45.2+ cells. Thymus sizes were: Ihh+/+: 4.8 × 103; Ihh+/−: 6.4 × 103; Ihh−/−: 4.8 × 103; and Ihh−/− Shh+/−: 6.0 × 103.