B-lymphocyte subsets in IgAN
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).
In the peripheral circulation of patients with IgAN, proportions of pre-switched B cells and plasmablasts were lower than those in HC (p=0.005 and p=0.01 respectively), while the proportion of CD19-negative long-lived plasma cells (LLPC) was higher (p=0.02, Fig. 2). There were no significant differences between patients with IgAN and HC comparing the proportions of naïve B cells and switched B cells. To assess if these differences are IgAN- specific, the cell fractions in IgAN patients were compared to those in ADPKD. A significant difference between the groups was observed for pre-switched B cells but not for plasmablasts or LLPC (Fig. 2).
Since we observed a similar proportion of naïve B cells in HC and IgAN patients, despite the differences in pre-switched B cells, we also analyzed the ratio between naïve and pre-switched B cells. The ratio between naïve and pre-switched B cell proportions was higher in IgAN patients compared to HC (p=0.02) and ADPKD (p=0.02) (Fig. 3).