To determine whether factors related to disease activity determine changes in the glycosylation of alpha 1-acid glycoprotein (AGP) observed at the early stage of rheumatoid arthritis (RA).
Using affinoimmunoelectrophoresis with the lectin concanavalin A (Con-A), the microheterogeneity of serum AGP was studied in patients with early (n = 54) and established (n = 46) RA and the results were expressed as reactivity coefficients (AGP-RC).
When compared with controls (n = 44), AGP-RC values were increased in the patients with very recent RA of no more than 3 months duration (p < 0.05), whereas normal or low AGP-Con-A reactivity was found in the patients with early RA with disease duration exceeding 3 months. In the entire group with early RA, the multiplicative model of regression described the relationship between AGP-Con-A reactivity and disease duration (p < 0.005). AGP variant with low binding affinity to Con-A predominated in the sera of patients with established RA and no relationship between the glycosylation profile of AGP and disease duration was observed in this group. When AGP-RC values were compared in the subgroups of patients with early and established RA with similar disease activity as measured by the Mallya-Mace score or erythrocyte sedimentation rate, there was a significant decrease in AGP-RC with increasing disease activity (p < 0.05).
In view of our findings, early RA begins as an acute inflammation with increase of AGP-Con-A reactivity and becomes chronic during the first year of the disease. Factors related to disease activity appear important in determining the rate at which RA enters a chronic phase.