CXCL8 and rheumatoid arthritis: Indeed, sTyro3 levels positively correlated with synovial fluid levels of TNF-α (r = 0.55, P = 0.01), IL-1β (r = 0.60, P = 0.009), CXCL8/IL-8 (r = 0.57, P = 0.009), and IL-10 (r = 0.69, P = 0.007) (Figures 4(a) – 4(d)), but not with IL-6 (r = 0.22, P = 0.36) (Table 2) in RA patients.