Synovial fluid beta 2 microglobulin and hydroxyproline fractions in rheumatoid arthritis and nonautoimmune arthropathies.

Fourteen patients with classical and definite seropositive rheumatoid arthritis (RA), 5 patients with microcrystalline arthritis, and 7 patients with osteoarthrosis were studied with respect to markers of newly synthesised collagen (synovial NDOH pro levels); markers of connective tissue resorption (synovial DOH pro and NBH levels); markers of lymphoid tissue activity (synovial and plasma beta 2m levels). Higher amounts of NDOH pro in RA synovial fluid are compatible with the hypothesis of a local connective tissue production as suggested by Uitto et al. on basis of a higher protocollagen proline hydroxylase activity in RA synovial tissue. DOH pro and NBH do not differ significantly in synovial fluid from RA or gouty patients, but the correlations between these forms of OH pro and, respectively, synovial lymphocytes and polymorphonuclear leucocytes are indicative of different processes of connective tissue remodelling in the 2 conditions. Synovial beta 2m levels are a direct function of total synovial lymphocyte counts independently of the type of arthropathy being explored. The ratio of synovial to plasma beta 2m is systematically above unity in RA patients only.