|Multiple factors influence the contribution of individual immunoglobulin light chain genes to the naïve antibody repertoire|
Background:The naïve antibody repertoire is initially dependent upon the number of germline V(D)J genes and the ability of recombined heavy and light chains to pair. Individual VH and VL genes are not equally represented in naïve mature B cells, suggesting that positive and negative selection also shape the antibody repertoire. Among the three member murine V?10 L chain family, the V?10C gene is under-represented in the antibody repertoire. Although it is structurally functional and accessible to both transcriptional and recombination machinery, the V?10C promoter is inefficient in pre-B cell lines and productive V?10C rearrangements are lost as development progresses from pre-B cells through mature B cells. This study examined VH/V?10 pairing, promoter mutations, V?10 transcript levels and receptor editing as possible factors that are responsible for loss of productive V?10C rearrangements in developing B cells.Results:We demonstrate that the loss of V?10C expression is not due to an inability to pair with H chains, but is likely due to a combination of other factors. Levels of mRNA are low in sorted pre-B cells and undetectable in B cells. Mutation of a single base in the three prime region of the V?10C promoter increases V?10C promoter function in pre-B cell lines. Pre-B and B cells harbor disproportionate levels of receptor-edited productive V?10C rearrangements.Conclusions:Our findings suggest that the weak V?10C promoter initially limits the amount of available V?10C L chain for pairing with H chains, resulting in sub-threshold levels of cell surface B cell receptors, insufficient tonic signaling and subsequent receptor editing to limit the numbers of V?10C-expressing B cells emigrating from the bone marrow to the periphery.
Fonte: BMC Immunology