To review and summarize the current findings regarding the characteristics of the B-cell receptor (BCR) repertoire in various rheumatic diseases (including SLE, RA, SSc, IIM, IgG4-RD, vasculitis, JIA, and pSS), and to discuss the clinical significance of BCR repertoire analysis in evaluating treatment response, disease remission, and progression.

Researchers synthesized findings from multiple published studies that utilized high-throughput sequencing, BCR repertoire analysis, and single-cell RNA sequencing to investigate B-cell dynamics. The reviewed studies compared BCR characteristics such as:Immunoglobulin gene usage (IGHV, IGHJ, IGKV);CDR3 length and amino acid composition;Clonal expansion and diversity;Somatic hypermutation (SHM) levels;Isotype switching patterns;Treatment effects (rituximab, glucocorticoids, immunosuppressants, IVIG)

The review presents disease-specific BCR repertoire findings: In systemic Lupus Erythematosus : Glucocorticoids reduced IGHV3 family usage but did not alter IGHV–IGHJ pairing or overall autoantibody clone percentage. Rituximab preserved IGHV/DH/JH repertoire but increased somatic mutations; persisting B cells were isotype-switched (IgG1/IgG2) and clonally expanded. BAFF blockade reduced diversity and increased clonality in mouse models.In rheumatoid arthritis : Frequent *IGHV4-34* and *IGHV1-69* usage, longer CDR3 regions linked to autoreactivity, and higher clonal expansion compared to healthy controls. Rituximab increased clonal expansion and mutation load; early BCR repopulation correlated with later therapeutic response.In systemic sclerosis: Increased *IGHV3-9* and IGHJ4 usage, shorter average CDR3 length, and high BCR diversity overall. Rituximab caused transient diversity loss with increased class switching in remaining B cells.In idiopathic inflammatory myopathy: IVIG responders showed emergence of new dominant BCR clones and loss of pretreatment clones; decreased cumulative clone frequency correlated with clinical improvement.In IgG4-Related Disease: IgG4+ clones dominated the peripheral blood IgG+ repertoire and matched clones in affected tissues; glucocorticoids rapidly suppressed these clones.In systemic vasculitis: EGPA showed increased IgE/IgG3 and IGHV4 usage; Behçet’s disease showed IgA dominance and IGHV1 family overexpression; clonality and class-switching patterns varied by subtype.In juvenile idiopathic arthritis : Greater dominant clone expansion and lower BCR diversity compared to healthy controls.as for primary Sjögren’s syndrome: Biased IGHV4 usage, higher clonal similarity between labial glands and peripheral blood, and correlation of κ/λ light chain usage with disease activity.

The BCR repertoire serves as a critical biomarker in Rheumatic diseases, with distinct characteristics observed across different conditions and treatment responses. Disease-specific signatures: Unique patterns of IGHV gene usage, CDR3 length, and isotype distribution exist across diseases (e.g., *IGHV4-34* in RA, *IGHV3-9* in SSc, increased IgE/IgG3 in EGPA).Treatment monitoring: Changes in BCR diversity, clonality, and isotype switching correlate with treatment sensitivity and clinical outcomes. For example, BCR repopulation timing predicts response to rituximab in RA, while suppression of IgG4+ clones reflects glucocorticoid efficacy in IgG4-RD.Predictive potential: BCR repertoire features (e.g., dominant clone frequency, class-switching patterns) may serve as predictors of therapeutic sensitivity and disease progression.