TNFSF11 and rheumatoid arthritis: In addition, it activates synovial fibroblasts to express matrix metalloproteinases and receptor activator of nuclear factor-κB ligand (RANKL), which induces the differentiation of osteoclasts contributing to bone resorption and bone erosions.3 4 Tocilizumab (TCZ) is a humanised monoclonal antibody against IL-6 receptor, approved for the treatment of active RA both as monotherapy and in combination with methotrexate.