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.