F2RL1 and rheumatoid arthritis: When we compared the expression of PAR2 within the cell populations, OA patients had elevated levels of PAR2 in the total monocyte/macrophage group compared to both PsA (p=0.014) and RA (p=0.046), evident particularly in the intermediate monocyte/macrophage subset (p=0.008 vs. PsA; Figure 2B).