CD19 and autosomal dominant polycystic kidney disease: Based on the expression of the cell surface markers CD19, CD27, CD38 and IgD, the following B cell subsets were identified in the peripheral blood of patients with IgAN, ADPKD and HC: naïve B cells (CD19+ CD27-, IgD+), pre-switched B cells (CD19+ CD27+ IgD+), switched B cells (CD19+ CD27+ IgD-) plasmablasts (CD19+ CD27+ CD38+) and long-lived plasma cells (CD19-CD27hi CD38hi).