Although the origin and function of DN B cells remain unclear, it was suggested that DN B cells may be exhausted memory B cells (48), or precursor memory B cells that have not yet to upregulate CD27 (49), or a product which CD27 fails to upregulate appropriately (50) and the increased DN B cells in SLE patients were considered as precursors of autoantibody producing plasma cells (51). This evidence concerns the gene CD27 and systemic lupus erythematosus.