CD4 and rheumatoid arthritis: Tregs activation and expansion in parallel with PD1 signalling are critical for the maintenance of CD4+ T‐cell homeostasis and elimination of either can result in its breakdown.32 Dysregulation of the PD1 pathway can be an important contributor to autoimmune pathogenesis, as has been shown in rheumatoid arthritis (RA), systemic lupus erythematosus, and multiple sclerosis (MS).33, 34, 35, 36, 37, 38 Furthermore, PD1 and its ligand PDL1 were reported to be decreased in the PBMCs of ITP patients, which suggested the important role of the PD1 pathway in the pathogenesis of ITP.39