Microheterogeneity of acute phase proteins in patients with clinically active and clinically nonactive osteoarthritis

Summary Microheterogeneity of two acute phase glycoproteins, -1-acid glycoprotein (AGP) and -1-antichymotryspin (ACT), concentrations of AGP, ACT, and C-reactive protein (CRP), and levels of three cytokines: interleukin 1 (IL-1-), interleukin 6 (IL-6), and tumor necrosis factor (TNF-) were determined in 61 serum samples and 7 synovial fluids (SFs) obtained from patients (n=61) with osteoarthritis. Using affinity immunoelectrophoresis with concanavalin A (conA), a significant decrease in the reactivity of AGP and ACT with this lectin was found in patients with clinically active osteoarthritis when compared to those with clinically nonactive disease (p<0.001 and p<0.05, respectively). There was no increase in the concentration of AGP, ACT, and C-reactive protein (CRP) in the sera examined. In particular, no increase in the serum level of these proteins was found in the patients with clinically active disease. Low concentrations of IL-6 and TNF- were found in most sera and SFs examined. In 6 out of 7 SFs available, IL-6 concentrations were higher than in the respective serum samples but for TNF- the same could be shown in one case only. Low concentrations of IL-1- were found in 4 serum samples obtained from patients with clinically active osteoarthritis and in no SF specimen studied. In the entire group, serum level of TNF- correlated weakly with the AGP and ACT reactivity coefficients with conA (r=0.3634, p<0.005 and r=0.3324, p<0.02, respectively).Our findings suggest that there are changes in the microheterogeneity of acute phase glycoproteins in some patients with osteoarthritis similar to those observed in rheumatoid arthritis and other chronic inflammations. Possible mechanisms of the involvement of cytokines in the regulation of glycosylation of acute phase glycoproteins in osteoarthritis are discussed.