Altered B cells homeostasis in child-onset immunoglobulin A vasculitis

Abstract

46Background: Immunoglobulin A vasculitis (IgAV), also called Henoch-Schönlein purpura, is 47 a systemic small vessels vasculitis with immunoglobulin A1-dominant immune deposits. B-48 cells are a heterogeneous population with unique subsets distinguished by their phenotypes and 49 cytokine production. Here, we explored the status of B cell subsets in patients with IgAV. 50 Methods: Thirty IgAV patients and fifteen age-and sex-matched healthy individuals were 51 enrolled in this study. Fresh blood samples were collected from both healthy and IgAV patients. 52 Upon the distinct expressions of CD3, CD19, CD20, CD38, CD27 and IgD, peripheral blood 53 mononuclear cells (PBMCs) were initially categorized into plasmablasts and memory B cells. 54 Subsequently, using surface markers including CD138 and IgM, and intracellular markers 55 containing IgM and IgG, plasmablasts and memory B cells were further divided into distinct 56 subgroups. A total of eleven populations were detected using multiple flow cytometry. 59 HCs. Only CD3 -CD19 + IgD -CD27 + IgM + B cell counts were reduced in IgAV. The elevated B 60 cell numbers returned to normal after treatment. Plasma and plasmablast B cell numbers 61 correlated with plasma IgA levels. On the contrary, CD3 -CD19 + IgD -CD27 + IgM + B cell 62 numbers were negatively proportional to the plasma IgA levels while naïve B cell numbers 63 correlated with plasma and plasmablast B cell counts.64 Conclusions: We hypothesized that immunoglobulin production was abnormally elevated in 65 IgAV and could be explained by altered B-cell subset homeostasis.66