CD19 and systemic lupus erythematosus: Characterized by the induction of T-bet-driven double-negative 2 (CD27−, IgD−, CD11c+, CD21− (DN2)) B cells, expansion of CD19+ antibody-secreting cells (ASCs) and depression of mutation frequencies in the ASC repertoire, these responses are highly similar to those we had identified previously in patients with active severe systemic lupus erythematosus (SLE)13,20.