Fcγ receptor expression levels on monocytes are elevated in rheumatoid arthritis patients with high erythrocyte sedimentation rate who do not use anti-rheumatic drugs

Abstract

Objectives. Levels of immunoglobulin G (IgG) Fc receptors (FcγRs) affect the activity and function of monocytes/macrophages when binding IgG-containing immune complexes. Hence, the expression level of FcγRs on monocytic cells may influence inflammation in patients with rheumatoid arthritis (RA). In this study the expression levels of FcγRI, IIa and IIIa on peripheral blood monocytes of RA patients were compared with those of healthy controls and related to patient and disease characteristics and the use of disease-modifying anti-rheumatic drugs (DMARDs). In addition, FcγR expression levels were determined on RA synovial fluid macrophages and compared with those in RA peripheral blood. Methods. Mononuclear cells from peripheral blood and synovial fluid were isolated and FcγR expression levels on CD14-positive cells were analysed by flow cytometry. The effects of patient and disease characteristics and the use of DMARDs were assessed. Results. A high expression level of FcγRIIa and high percentages of FcγRIIIa-expressing monocytes were found in RA patients with a high erythrocyte sedimentation rate. DMARD-naive early RA patients had higher FcγRIIa expression levels but a similar amount of FcγRIIIa-positive monocytes compared with RA patients using DMARDs. In synovial fluid, FcγRIIa expression levels were lower than in RA peripheral blood, whereas the percentage of FcγRIIIa-positive monocytic cells was higher in synovial fluid than in peripheral blood. Conclusions. These data point to the involvement of FcγRs, specifically FcγRIIa and IIIa, in the immune response of RA and suggest that FcγR expression levels are susceptible to modulation by DMARD therapy.