TNF and rheumatoid arthritis: First, we observed an increased basal secretion of pro-inflammatory cytokines interleukin (IL)-6 and tumour necrosis factor (TNF) in peripheral blood RA neutrophils in contrast to neutrophils from healthy controls (IL-6: 0.29 (0.26–0.35) vs. 0.04 (0.03–0.08), pg/ml; p < 0.001 and TNF: 0.33 (0.23–0.47) vs. 0.07 (0.03–0.14), pg/ml; p < 0.01) (Fig. 5a).