SAT-387 B LYMPHOCYTE SUBSET CHANGES IN PRIMARY MEMBRANOUS NEPHROPATHY

Abstract

Primary membranous nephropathy (PMN) is the most common cause of nephrotic syndrome in adults. Rituximab a chimeric monoclonal anti-CD20 antibody has been supposed to eliminate autoantibody-producing B cells via direct signaling, complement-mediated cytotoxicity (CMC), and antibody-dependent cellular cytotoxicity. According to the fact that a wide range of B lymphocytes may carry this marker, we aimed to identify which subset is more(or less) frequent in PMN patients and which one is more affected by rituximab administration. Three groups were enrolled, included a healthy control group and two patient groups having the clinical, laboratory, and pathological diagnostic criteria of PMN, comprising either patients on standard treatment or patients on standard treatment plus rituximab. The latter group was studied just before receiving rituximab (pre-rituximab) and two months later (post rituximab). Peripheral blood mononuclear cells (PBMCs) were isolated using Ficoll-hypaque (inno-train, Germany) gradient. Afterward, cells stained with mouse antihuman CD19-Cy5-conjugated antibody (Cytognos, Spain), mouse antihuman CD24-PE-conjugated antibody (Cytognos, Spain), and mouse antihuman CD38-FITC-conjugated antibody (Cytognos, Spain). In post-rituximab analysis, CD19+ cell count showed notable reduction (P value = 0.003) B CD19+CD24+CD38- cells, representing the memory B cell population, did not show any significant difference between healthy controls and patients. Furthermore, the count of these cells did not decrease significantly two months after rituximab administration. The subset of CD19+CD24-CD38+ B lymphocytes, a class of naïve/mature lymphocytes with normal function, was significantly higher in the control group than in standard treatment patients (P value = 0.01). However, no statistically significant difference was found in CD19+CD24-CD38+B lymphocytes neither between the rituximab and control groups nor between pre-rituximab and post-rituximab patients. Left Panel:CD19+CD24highCD38high cells frequency (percentage in CD19+ cells) in four groups of standard treatment (steroid + immunosuppressive), pre-rituximab (steroid + immunosuppressive + rituximab), post-rituximab (two months after RTX administration), and healthy controls; *P < 0.05 **P < 0.001 ***P < 0.0001 The number of regulatory B cells decreased in both standard treatment and rituximab-receiving PMN patients and the proportion of naïve/mature B-lymphocytes was lower in the former group. Moreover, the memory B cells count did not reduce significantly two months after rituximab administration. Hence, it might be the best choice to target the memory B cell subset in immunosuppressive therapy while avoiding the Breg or naïve/mature B lymphocyte depletion to obtain more favorable sustained outcomes.