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. [ABSTRACT FROM AUTHOR]