The surrogate light chain in B-cell development.

The proteins encoded by the VpreB and lambda 5 genes associate with each other to form a light (L) chain-like structure, the surrogate L chain. It can form Ig-like complexes with three partners-the classical heavy (H) chain, the DHJHC mu-protein, or the newly discovered p55 chain; these are expressed on the surface of pre-B cells at different stages of development. Here, Fritz Melchers and colleagues review the structures of the VpreB and lambda 5 genes in mouse and their relatives in humans, describe their pattern of expression, and speculate on their possible evolution and functions.