Surrogate or conventional light chains are required for membrane immunoglobulin mu to activate the precursor B cell transition

Abstract

To examine the role of light chains in early B cell development we combined RAG-1 and λ5 mutations to produce mice that expressed neither conventional nor surrogate light chains (RAG-1 , λ5). Unique heavy and light chain genes were then introduced into the double and single mutant backgrounds. Membrane immunoglobulin (Ig)μ (mlgμ) associated with Igα- Igβ but was unable to activate the pre B cell transition in RAG-1 λ5 mice. Either λ5 or kappa light claims were sufficient to complement this deficiency. Therefore light chains are absolutely required for a functional Ig signaling module in early B cell development. Our data provide direct evidence for the existence of two pathways for induction of early B cell development one which is activated through surrogate light claims and mlgμ, and an alternative pathway which uses conventional light chains and mlgμ.