PDCD1 and rheumatoid arthritis: Additionally, the expression of markers related to chronic TCR activation (PDCD1, CTLA4, and ICOS), and cytokines (TNF, IFNG, and GZMB) were significantly increased in RA compared to OA (Figure 2—figure supplement 2D), in line with what we observed in JIA SFMC (Figure 2A/B).