Neopterin production in inflamed knee joints: high levels in synovial fluids.

Neopterin levels of serum and fluid were determined in 30 patients with inflammatory synovial fluids and in 30 controls with joint effusions induced by trauma or osteoarthritis. Neopterin was significantly elevated in inflammatory fluids. There was no correlation with the acute phase reactants. Neopterin levels were significantly higher in inflammatory fluids than in serum, and vice versa in non-inflammatory conditions. Our results indicate that in arthritis neopterin is produced locally in the joint by monocytes induced by T-cell activation.