IFNG and reactive arthritis: In an important early study, the authors showed that the T cell cytokine pattern detected in the synovial membrane of patients with rheumatoid arthritis (RA) and reactive arthritis (ReA) differs regarding the expression of cytokines such as interferon gamma (IFNγ) and interleukin (IL)‐4 [11] according to the T helper cell (Th)1/Th2 paradigm [12].