TNF and rheumatoid arthritis: Moreover, the anti-inflammatory effect was diminished in RA-SF compared with OA-SF, and the anti-inflammatory activity of PK2 in OA-SF and the reduced anti-inflammatory effect of PK2 in RA-SF (Fig. 6 and Supplemental Fig. S1) were accompanied by an upregulation of PKR1 in TNFα-prestimulated OA-SF (Fig. 4).