Figure 1.

Attenuated pre-BCR-mediated prosurvival signalling through Erk1/2 affects central B cell selection. (A–C) Multicolour flow cytometric classification of Syk^+/+, Syk^+/Zap-70 (ctrl) and Syk^{Zap-70/Zap-70} (ki) bone marrow B cell subsets according to the Hardy fractionation scheme (A=pre-pro, B=early pro, C=late pro/large pre, D=small pre, E=immature, F=transitional). (D) Total bone marrow cell numbers and (E) B cell subset statistics; the partial pro- to pre-B cell transition arrest significantly affected bone marrow cellularity. (F) λ5 expression on B220⁺CD43⁺ B cells indicated comparable pre-BCR levels between ctrl and ki cells. (G, left) Analysis of functional cell blast formation by assessment of the forward scatter (FSC) profiles of pre-pro, pro- and pre-B cells. (G, right) Pre-B cell forward scatter statistics. (H) DNA content-based (Hoechst 33342) cell cycle analysis of B220⁺CD43⁺BP1⁺CD24⁺ pre-B cells using five-colour flow cytometry; numbers indicate representative percentages of pre-B cells in S/G2/M phase. (I) Total p42/p44 (Erk1/2) and phospho-p42/p44 (pErk1/2) levels of bone marrow cells left untreated (−) or treated (+) with anti-CD79b (Igβ) for 2 min at 37°C. *P<0.05, **P<0.01, ***P<0.001; n=8 (A–E, G) and three (F, H, I) per group; error bars indicate means±s.e.m. arb.u., arbitrary units; co, isotype control; Ig, immunoglobulin; ns, not significant. Figure source data can be found with the Supplementary data.