A Lower Proportion of Regulatory B Cells in Patients with Henoch–Schoenlein Purpura Nephritis

BACKGROUND: Henoch—Schoenlein purpura is the one of most common types of systemic vasculitis that involves impaired renal function and Henoch-Schoenlein purpura nephritis (HSPN). The diagnosis of this condition is largely based on immunohistologic detection of immunoglobulin A1-containing immune complex in the glomerular deposits of mesangium. Despite clinical advances, the etiopathogenesis of HSPN is still largely unknown. METHODS: In this study, we enrolled 25 newly diagnosed HSPN patients and 14 healthy controls. Then, fractions of B cell subtypes were determined in venous blood using flow cytometry. The serum interleukin (IL)-10 concentration was determined by enzyme-linked immunosorbent assay. RESULTS: Compared to those in healthy controls, the numbers of CD38(+)CD19(+), CD86(+)CD19(+), CD38(+)CD86(+)CD19(+), and CD95(+)CD19(+) B cells per microliter of blood were significantly higher in HSPN patients. In contrast, the numbers of CD5(+)CD19(+), IL-10(+)CD19(+), CD5(+)CD1d(+)CD19(+), and IL-10(+)CD5(+)CD1d(+)CD19(+) B cells per microliter of blood and the serum IL-10 concentration were significantly lower in HSPN patients. Following treatment, the numbers of CD38(+)CD19(+) and CD86(+)CD19(+) B cells per microliter of blood were significantly reduced in HSPN patients. However, the numbers of CD5(+)CD1d(+)CD19(+), CD5(+)CD1d(+)IL-10(+)CD19(+), and IL-10(+)CD19(+) B cells per microliter of blood and the serum IL-10 concentration were significantly increased in HSPN patients following treatment. The estimated glomerular filtration rate (eGFR) was negatively correlated with the number of CD38(+)CD19(+) B cells but positively correlated with the numbers of IL-10(+)CD19(+), CD1d(+)CD5(+)CD19(+), and IL-10(+)CD1d(+)CD5(+)CD19(+)B cells per microliter of blood and the serum IL-10 concentration. The 24-h urinary protein concentration was positively correlated with the number of CD38(+)CD19(+)B cells but negatively correlated with the numbers of IL-10(+)CD19(+), CD1d(+)CD5(+)CD19(+), and IL-10(+)CD1d(+)CD5(+)CD19(+)B cells per microliter of blood and the serum IL-10 concentration. CONCLUSION: Our results suggest that CD38(+)CD19(+) and CD1d(+)CD5(+)CD19(+) B cells (Bregs) contribute to the pathogenesis of HSPN.