CD19 and systemic lupus erythematosus: They found that CXCR5− DN cells are enhanced in SLE patients compared to HCs, but only the frequency of those expressing low levels of CD19 correlates with plasmablast frequencies and shows higher levels of IRF4 (Interferon Regulatory Factor 4), PRDM1 (PR Domain Zing Finger Protein 1), and XBP1 (X-Box Binding Protein 1) [42].