CD19 and systemic lupus erythematosus: This paper investigates whether T-bet+ B cells, as well as age-associated B cells/ABCs (CD19+CD21-CD11c+T-bet+) and double-negative B cells/DN (CD19+IgD-CD27-CXCR5-T-bet+), serve as prognostic and/or therapeutic tools for systemic lupus erythematosus (SLE) in humans.