PDCD1 and rheumatoid arthritis: demonstrated increased expression of inhibitory receptors programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) in CD4+ T cells from RA patients (19), while another study in ANCA-associated vasculitis patients revealed dysregulated expression of Tex-related genes in CD8+ T cells (20).