Aberrant FcγRIIb and FcγRIII expression on monocytes from patients with Behçet's disease

Behçet's disease (BD) patients have abnormal FcγR polymorphisms, the implication of which remains elusive. We examined FcγRIIb expression on neutrophils, monocytes, B cells, natural killer cells, dendritic cells and T cells, and FcγRI and FcγRIII expression on monocytes in BD patients and healthy controls using flow cytometry. We further stimulated monocytes with IgG and (or) lipopolysaccharide (LPS) and measured IL-6 and TNF-α production by enzyme-linked immunosorbent assay. We found that BD monocytes expressed a lower level of FcγRIIb and a higher level of FcγRIII, which were correlated with erythrocyte sedimentation rate and C-reactive protein and were rescued after treatment. Furthermore, LPS- and IgG-stimulated BD monocytes produced higher levels of IL-6 and TNF-α than HC monocytes. In summary, we found that BD monocytes downregulated FcγRIIb expression and upregulated FcγRIII expression, which were correlated with disease activity and potentially contributed to monocyte hyperactivation in BD.