Asynchronous replication and allelic exclusion in the immune system

The development of mature B cells involves a series of molecular decisions which culminate in the expression of a single light-chain and heavy-chain antigen receptor on the cell surface1,2. There are two alleles for each receptor locus, so the ultimate choice of one receptor type must involve a process of allelic exclusion. One way to do this is with a feedback mechanism that downregulates rearrangement after the generation of a productive...