Detailed B-cell maturation analysis performed on BM from case 11. (A) Bar chart displays proportion of B cells at different stages of maturation within the BM compartment as determined by flow cytometric analysis. The bottom bar is from child 11 aged 8 months, demonstrating a leaky maturation block before the cytoplasmic Igμ-positive pre-B-II cell stage. The middle bar shows repeat analysis in the same patient 10 months after BMT, at which time the pattern had reverted to that observed in age-matched normal controls (top bar). (B) Relative proportions of B cells at different maturation stages in BM samples before and after BMT (analysis performed by M. van der Burg and J. J. M. van Dongen [Erasmus Medical Center, Rotterdam, The Netherlands]).