PDCD1 and rheumatoid arthritis: This study aimed to determine whether T cell activation and subset-associated cytokines differentially regulate the expression of PD-ligand 1 (PD-L1) and PD-L2 on FLS from RA patients compared with non-inflammatory (NI) controls, and whether PD1 engagement induces distinct transcriptional downstream responses in RA-FLS versus NI-FLS.<h4>Methods</h4>Primary FLS cell lines were cultured from synovial tissue of patients with established RA or NI controls undergoing arthroscopy due to previous injury.