CXCR5 and systemic lupus erythematosus: In SLE:↑IgD-CD27+ B cells↑IgD-CD27- atypical mB cellsAmong DN and switched mB cells:↓† BTLA↑ CXCR5+CD19 intermediate↑ CXCR5-CD19low (novel)↑CXCR5-CD19high