In particular, the salient role of immune cell dysfunction in RA pathogenesis indicates the programmed cell death protein-1 (PD1)/programmed death-ligand 1 (PD-L1) axis is an attractive candidate for gene therapy given that the binding of PD-L1 to the PD1 receptor on lymphocytes results in immune cell suppression (12). Here, PDCD1 is linked to rheumatoid arthritis.