For years it has been known that B lymphocytes express either IgM and IgM/IgD. It was unknown how B cells are triggered to express IgD additionally. A paper in PNAS  (doi: 10.1073/pnas.1402739111) now demonstrates that a so far overlooked Zinc-finger protein (ZFP318) is responsible for the alternative splicing in the B cell thus driving expression of IgD.