The Role of B cells in Idiopathic Inflammatory Myopathies

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of autoimmune disorders characterized by skeletal muscle inflammation and systemic immune activation. Although traditionally viewed as T cell-driven diseases, recent evidence suggests that B lymphocytes may also contribute to disease mechanisms through both antibody-dependent and noncanonical pathways. Beyond their role in autoantibody production, B cells might influence immune regulation by modulating cytokine networks, presenting antigens, and interacting with T cells and stromal elements within inflamed tissues. These findings have prompted renewed interest in understanding B cell heterogeneity and its possible impact on the initiation and maintenance of chronic inflammation in IIM. However, the exact contribution of these cells to tissue damage and clinical variability remains uncertain. Advances in high-dimensional cytometry, transcriptomics, and tissue profiling are beginning to delineate distinct B cell signatures associated with disease activity, yet the causal links to pathogenesis remain unclear. The observed clinical benefit of B cell-depleting therapies, though variable among patients, reinforces their potential relevance while underscoring the complexity of immune interactions in IIM. This review aims to synthesize current knowledge on B cells in IIM and to discuss how emerging mechanistic insights could refine our understanding of disease heterogeneity and guide future therapeutic approaches.