IL6R and rheumatoid arthritis: Tocilizumab (TCZ) is a first-in-class recombinant humanized monoclonal antibody against the IL-6 receptor (IL-6R), which has been marketed as a treatment for Castleman’s disease, moderate to severe active rheumatoid arthritis (RA) in adults, and juvenile idiopathic arthritis (Sheppard et al., 2017).