FIGURE 1.

mTOR signaling is normally activated in early B cell development and is decreased in Raptor-deficient mice. (A) Diagram of mouse B cell developmental stages with Hardy fraction notations (9). (B) BM B cells corresponding to Hardy fractions A–C′ (B220⁺CD43⁺), D (B220⁺CD43⁻IgM⁻), E (B220^loCD43⁻IgM⁺), and F (B220^hiCD43⁻IgM⁺) were purified from six WT mice and pooled. Immunoblotting was performed using Abs with specificity for the indicated proteins. β-actin was used as a loading control. (C) CD19⁺IgM⁻ BM cells were isolated from two Raptor-null and two WT control mice. Immunoblotting was performed using Abs with specificity for the indicated proteins.