CD19 and autoimmune disease: Sub-populations of T-bet+ B cells, known in the literature as age-associated B cells/ABCs (CD19+CD21−CD11c+T-bet+) and/or double-negative B cells/DN (CD19+IgD−CD27−CXCR5−T-bet+), expand in various autoimmune diseases, including systemic lupus erythematosus (SLE), and drive their pathogenesis [3, 4].