SPN and systemic lupus erythematosus: In fact, a small population of human blood CD20+CD27+CD43+IgD+/− B cells, which includes such PB precursors as well as a unique population exercising function akin to murine B1 cells [38,39], was found to be increased in SLE [40], and may contribute to the increase of median CD38 expression in CD27+ B cells in SLE.