Immunological heterogeneity in rheumatoid arthritis: challenges in early-stage stratification, non-response to targeted therapy, and the restoration of immune tolerance.

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic erosive synovitis, progressive bone destruction, and marked inter-patient heterogeneity in disease course and treatment response. This review critically examines the mechanisms underlying RA immunological heterogeneity, including genetic susceptibility, epigenetic regulation, autoantibody diversification, synovial pathotypes, and gut-joint axis-related immune-metabolic interactions. We further discuss how peripheral blood multi-omics, synovial molecular pathology, and biopsy-driven clinical trial evidence may inform early stratification and prediction of primary non-response. Rather than proposing a deterministic precision-medicine model, this review emphasizes an evidence-weighted framework in which molecular and tissue-level biomarkers are integrated with clinical phenotype and longitudinal treatment response. Emerging approaches, including pharmacomicrobiomics, local drug delivery, nanomedicine, and cell-based therapies, are evaluated as investigational strategies that require further validation. Overall, this review highlights how a more critical understanding of RA heterogeneity may improve patient stratification and support more rational therapeutic selection.