“…We can speculate that the prevalent detection of IL-23 in serum from both RA and PsA patients mirrors the systemic inflammatory response as demonstrated by its correlation with CRP levels in RA. On the contrary, higher SF levels of IL-6, IL-17 and TNF-α support the hypothesis of their major contribution locally, in joint inflammation, at the target tissue [32,33]. Statistically significant higher serum levels of IL-17 were observed in PsA than in RA, probably due to the elevated frequencies of IL-17 and IL-22 producing CD4+ T cells in PsA [34].…”