Cutting edge:: The PI3K p110δ is required for down-regulation of RAG expression in immature B cells

At the immature B cell stage the BCR signals the down-regulation of the RAG genes and Ig L chain (LC) allelic and isotype exclusion. The signaling pathway that regulates these events is poorly characterized. We demonstrate that immature B cells from mice deficient in the PI3K catalytic subunit p110 delta fail to suppress RAG expression and inappropriately recombine K and A LC loci. In addition, in the presence of the autoantigen, clonal deletion and receptor editing still takes place, demonstrating that these processes are independent of p110 delta. These results demonstrate a role for p110 delta in the regulation of RAG gene expression and thereby LC alleliclisotype exclusion. The journal of Immunology, 2007,178:1981-1985.