Members of the tumor-necrosis factor-α(TNF-α) and TNF-α receptor(TNFR) superfamilies of proteins(TNFSF and TNFRSF, respectively) play important roles in the function of the immune system. Decoy receptor 3(Dc R3, TNFRSF6b) is a decoy receptor that binds to three TNFSF ligands, Fas L, LIGHT and TL1 A. Association to these ligands competes with the corresponding functional receptors and blocks downstream signaling, leading to immunomodulatory effects, including the prevention of apoptosis. Dc R3 lacks a transmembrane region and exists only as a secreted protein, which is detectable in biological fluids. Recent studies have shown that Dc R3 is upregulated and may be pathogenetically implicated in several and diverse chronic inflammatory diseases. The strongest associations have been described for rheumatological diseases, mainly systemic lupus erythematosus and rheumatoid arthritis, inflammatory bowel disease, and serious infectious conditions, including systemic inflammatory response syndrome. In the majority of these conditions, Dc R3 m RNA and protein expression is elevated both at the target tissues as well as in the systemic circulation. Dc R3 concentration in the serum is untraceable in the majority of healthy individuals but can be detected in patients with various inflammatory diseases. In mostsuch cases, soluble Dc R3 correlates with disease severity, as patients with severe forms of disease have significantly higher levels than patients with milder or no activity. In addition, effective anti-inflammatory treatment leads to the disappearance of soluble Dc R3 from the circulation. Taken together, current evidence suggests that serum Dc R3 may become a useful biomarker for chronic inflammatory disorders, as it is upregulated in response to inflammatory stimuli, and may serve both as a prognostic marker for disease severity and as a surrogate indicator of response to treatment. Members of the tumor-necrosis factor-α (TNF-α) and TNF-α receptor (TNFR) superfamilies of proteins (TNFSF and TNFRSF, respectively) play important roles in the function of the immune system. Decoy receptor 3 (Dc R3, TNFRSF6b) is a decoy receptor that binds to three TNFSF ligands, Fas L, LIGHT and TL1 A. Association to these ligands competes with the corresponding functional receptors and blocks downstream signaling, leading to immunomodulatory effects, including the prevention of apoptosis. Dc R3 lacks A transmembrane region and exists only as a secreted protein, which is detectable in biological fluids. Recent studies have shown that Dc R3 is upregulated and may be pathogenetically implicated in several and diverse chronic inflammatory diseases. The strongest associations have been described for rheumatological diseases, mainly systemic lupus erythematosus and rheumatoid arthritis, inflammatory bowel disease, and serious infectious conditions, including systemic inflammatory response s yndrome. In the majority of these conditions, Dc R3 m RNA and protein expression is elevated both in the target tissues as well as in the systemic circulation. Dc R3 concentration in the serum is untraceable in the majority of healthy individuals but can be detected in patients with various inflammatory diseases. In mostsuch cases, soluble Dc R3 correlates with disease severity, as patients with severe forms of disease have significantly higher levels than patients with milder or no activity. In addition, effective anti-inflammatory treatment leads to the disappearance of Taken together, current evidence suggests that serum Dc R3 may become a useful biomarker for chronic inflammatory disorders, as it is upregulated in response to inflammatory stimuli, and may serve both as a prognostic marker for disease severity and as a surrogate indicator of response to treatment.