Synovial fluid mononuclear cells (SFMC) from ACPA− (n = 9) and ACPA+ (n = 12) RA patients were screened for the expression of these cytotoxic effector molecules and transcription factors in both CD4+ and CD8+ T cells by flow cytometry (Fig. 1, Supplementary Figs. 1a and 2, and Supplementary Data 1). This evidence concerns the gene CD8A and rheumatoid arthritis.