CD8A and rheumatoid arthritis: As expected, PMA/ionomycin greatly increased the expression of CD69 in most of the cells; however, a clear clustering of CD103-expressing cells could still be found and, concordant with our previous results, higher CD103 expression and increased frequency of CD103+ cells were observed in synovial CD8+ T cells from patients with PsA compared with RA (Figure 3A).