In the centre of RA pathogenesis, dendritic cells (DCs) play crucial roles in activation of CD4 lymphocytes by presenting proper T‐cell receptor stimulatory and co‐stimulatory signalling cues, and context‐dependent cytokines, polarizing them into several subsets of CD4 T cells including TH1 and TH17.8 The gene discussed is CD4; the disease is rheumatoid arthritis.