Unraveling BCR Repertoire Diversity and its Impact on Glucocorticoid Therapy in Pediatric Idiopathic Nephrotic Syndrome.

aimIdiopathic nephrotic syndrome (INS) is the most common glomerular disease in children, but its underlying mechanisms remain unclear. Although glucocorticoids (GC) are the first-line treatment, approximately 10% of INS cases are steroid-resistant (SRNS), and 50% may progress to refractory nephrotic syndrome (RNS). B cells play a crucial role in INS pathogenesis, treatment, and prognosis. This study aims to explore B-cell receptor repertoire (BCRR) characteristics in INS patients to identify molecular signatures associated with disease outcomes and develop early risk prediction models for RNS and SRNS.

methodsA case-control study was conducted using peripheral blood samples from 40 initial diagnosed INS patients and 56 age-matched healthy controls. BCRR was sequenced using dimer-avoided multiplex PCR, followed by Illumina NovaSeq sequencing. Immunoglobulin heavy chain (IGH) sequences were mapped and analyzed for diversity, clone expansion and shared clone, isotype usage, class-switch recombination (CSR), IGHV/J gene usage, CDR3 length and somatic hypermutation (SHM). Additionally, a prospective cohort study was conducted on INS patients, with BCRR measured at baseline and follow-up to track changes in response to treatment. Longitudinal analysis was performed to identify specific B-cell clones and predict treatment resistance.

resultsThe BCRR of INS patients exhibited lower evenness compared to controls, with significant increases in the usage of IGHM/D mutated and IgE/IgG12 isotypes. Public B-cell clones, including five specific CDR3 amino acid sequences, were identified across INS patients. NRNS patients showed increased clonal expansion with specific CDR3 sequences characters on IGHV5-51_IGHJ6 sequences and shorter CDR3 lengths, suggesting strong and focused autoimmune responses. In contrast, RNS and SRNS patients exhibited enhanced IgE-mediated immune responses, characterized by increased IgE BCRR diversity, decreased evenness and increased CSR. Early prediction models were developed based on BCRR parameters, successfully distinguishing between RNS and NRNS, SRNS and SSNS patients.

conclusionB-cell-mediated humoral immunity plays a pivotal role in INS pathogenesis, with distinct immune profiles associated with clinical outcomes. Non- refractory nephrotic syndrome (NRNS) patients exhibit clonal expansion with antigen-driven immune responses, whereas SRNS and RNS patients demonstrate persistent IgE-mediated responses that are resistant to GC but sensitive to second-line immunosuppressants. These findings offer new insights into the mechanisms of steroid resistance and provide a basis for early diagnosis and personalized treatment strategies in INS.