Surrogate Light Chain Expression Is Required to Establish Immunoglobulin Heavy Chain Allelic Exclusion during Early B Cell Development

AbstractAllelic exclusion at the IgH locus was examined in B lineage cells of wild-type mice and mice unable to express the surrogate light chain molecule λ5 using a single-cell PCR approach. By analyzing B precursor cells containing two VHDHJH rearrangements, we found that in wild-type animals, cells are allelically excluded as soon as μ chains are expressed. Furthermore, we provide evidence that in cells expressing Dμ proteins VH→DHJH rearrangement is inhibited. In contrast, in the absence of λ5 protein, B precursor cells were allelically “included,” indicating that allelic exclusion at the IgH locus requires expression of the pre-B cell receptor either containing a μ chain or a Dμ chain. However, although μ chain double-producing B precursor cells are generated in λ5-deficient mice, such cells were not detected among surface immunoglobulin positive B cells