Anti‐interleukin‐6 signalling therapy rebalances the disrupted cytokine production of B cells from patients with active rheumatoid arthritis

Rheumatoid arthritis (RA) is associated with abnormal B cell‐functions implicating antibody‐dependent and ‐independent mechanisms. B cells have emerged as important cytokine‐producing cells, and cytokines are well‐known drivers of RA pathogenesis. To identify novel cytokine‐mediated B‐cell functions in RA, we comprehensively analysed the capacity of B cells from RA patients with an inadequate response to disease modifying anti‐rheumatic drugs to produce cytokines in comparison with healthy donors (HD). RA B cells displayed a constitutively higher production of the pathogenic factors interleukin (IL)‐8 and Gro‐α, while their production of several cytokines upon activation via the B cell receptor for antigen (BCR) was broadly suppressed, including a loss of the expression of the protective factor TRAIL, compared to HD B cells. These defects were partly erased after treatment with the IL‐6‐signalling inhibitor tocilizumab, indicating that abnormal IL‐6 signalling contributed to these abnormalities. Noteworthy, the clinical response of individual patients to tocilizumab therapy could be predicted using the amounts of MIP‐1β and β‐NGF produced by these patients’ B cells before treatment. Taken together, our study highlights hitherto unknown abnormal B‐cell functions in RA patients, which are related to the unbalanced cytokine network, and are potentially relevant for RA pathogenesis and treatment. B cells from RA patients who failed conventional DMARD therapy displayed a broadly impaired cytokine production upon BCR activation, which was corrected following a 16‐weeks treatment with the IL‐6 receptor inhibitor tocilizumab. These results highlight novel abnormalities in B cell antibody‐independent functions that are related to IL‐6 signalling in RA.