Rescue of CFU-B colony formation in MBS-treated BtkTec^–/– mice. BM (A) and splenocytes (B) from individual animals were cultured with LPS and sheep red blood cells (SRBCs) in agar to induce B-cell colony formation. Colonies were enumerated at day 7 and data from all experimental cohorts are represented. The colony count for each animal (average of 2 plates) is shown and the mean for all animals in each experimental category is indicated by a bar. *Statistical difference between MBS-treated mice and mock-transduced (open symbols) or MIG-transduced (filled symbols) BtkTec^–/– controls (P < .000 05).