Cytidine deaminase and lactoferrin in inflammatory synovial fluids. Indicators of local polymorphonuclear cell function?

Cytidine deaminase (CD) is a cytoplasmatic enzyme present predominantly in polymorphonuclear cells (PMNC) in inflamed joints. Lactoferrin is situated in the secondary granules of PMNC and is released by secretory/phagocytic stimuli, whereas CD is released mainly upon cell lysis. To study the release of these molecules in arthritic conditions we measured CD and lactoferrin levels in synovial fluid (SF) drawn from patients with rheumatoid arthritis (RA), crystal pyrophosphate disease (CPPD), psoriatic arthropathy, reactive arthritis, spondylarthropathy, and osteoarthrosis. CD activity was highest in SF from RA and CPPD followed by psoriatic arthropathy, reactive arthritis and spondylarthropathy. Lactoferrin concentrations were highest in CPPD followed by RA, reactive arthritis, psoriatic arthropathy, and spondylarthropathy. Both CD and lactoferrin levels were low in osteoarthrosis SF. Although SF CD activity and lactoferrin levels correlated well in all diagnostic groups, the ratio between CD and lactoferrin was higher for RA, psoriatic arthropathy, and spondylarthropathy compared to reactive arthritis and CPPD. This suggests predominant release by PMNC lysis in the more chronic arthritis groups and more degranulation in the more episodic CPPD and reactive arthritis groups. CD activity and lactoferrin levels correlated significantly with SF cell counts in the RA and psoriatic arthropathy groups.