MO008B LYMPHOCYTE SUBSET CHANGES IN PRIMARY MEMBRANEOUS NEPHROPATHY

Abstract Background and Aims Primary membranous nephropathy (PMN) is the most common cause of nephrotic syndrome (NS) 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 (ADCC). 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. Method Three groups were enrolled in the present study. They 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 were adjusted to a concentration of 1 _ 106 cells/mL and 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). Flow cytometry performed by FACS Calibur (BDFacs Calibur Becton Dickinson, USA). Results The total lymphocyte percentage was higher in PMN patients receiving either standard treatment or rituximab than in healthy controls (standard-treatment vs. control: P value = 0.001, pre-rituximab vs. control: P value =0.001). 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. Conclusion 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.