Regulation of an early developmental checkpoint in the B cell pathway by Ig beta

Many of the cell fate decisions in precursor B cells and more mature B cells are controlled by membrane immunoglobulin (Ig)M heavy chain (mu) and the Ig alpha-Ig beta signal transducers. The role of Ig beta in regulating early B cell development was examined in mice that lack Ig beta (Ig beta-/-). These mice had a complete block in B cell development at the immature CD43+B220+ stage. Immunoglobulin heavy chain diversity (DH) and joining (JH) segments rearranged, but variable (VH) to DJH recombination and immunoglobulin messenger RNA expression were compromised. These experiments define an unexpected, early requirement for Ig(beta) to produce B cells that can complete VDJH recombination.