TNF and Sacroiliac arthritis: This analysis (ANOVA) revealed association of spontaneous cytokine production (IL-1β, P = 0.009; IL-6, P = 0.03; TNFα, P = 0.012) and FSL-1-induced IL-6 production (P = 0.007) with therapy—conventional treatment versus treatment with biologics (i.e., TNFα inhibitors)—but no association with disease state (i.e., presence of radiographic sacroiliitis).