[Macroglobulin alpha-2 in synovial fluid: relationship with reactants of the acute phase of rheumatoid arthritis]

Metalloproteinases (e.g. collagenase, elastase, stromelysin) are present in large amount in synovial fluid (SF) during rheumatoid arthritis (RA) and are actively involved in articular tissue damage. alpha 2-Macroglobulin (alpha 2M) functions as a "molecular trap" for proteinases and is considered the major inhibitor of metalloproteinases. We found increased concentrations of alpha 2M in SF of RA patients, significantly related to acute phase reactants, local inflammatory parameters and joint damage. The alpha 2M ratio between, RA SF and control SF, was found higher than between RA serum and control serum, indicating a selective localization and activity of alpha 2M in inflamed joint. The relationship between alpha 2M and the inflammatory parameters, including IL-6, is discussed.