PDCD1 and rheumatoid arthritis: To demonstrate molecular parallelism between RA natural history of disease and anti-PD-1 antibody-induced irAE, and to evaluate the status of PD-1 signaling in synovial tissue during the development of RA, the enrichment of Nivolumab upregulated gene signature [19] was interrogated in pre-RA and RA synovial biopsies by gene set variation analysis (GSVA).