Overexpression of CD64 on CD14++CD16- and CD14++CD16+ monocytes of rheumatoid arthritis patients correlates with disease activity.

It is well-known that monocytes are a heterogeneous cell population and different monocyte subsets play important roles in rheumatoid arthritis (RA). Cluster of differentiation (CD)64 is one of Fc receptor, which initiates immunological and inflammatory reactions. However, the roles in RA remain to be elucidated. In the present study, the expression of CD64, CD40, CD163, CD206, HLA-DR, CD80 and CD86 on monocytes and the expression of CD64 on monocyte subsets were determined by flow cytometry. The expression of CD64 on monocyte subsets in patients with RA was further analyzed for their correlation with markers of autoimmune response, inflammation, disease activity of RA and serum cytokines. Compared to the health volunteers, the expression of CD64 on monocytes and each monocyte subset were significantly elevated in RA patients. The expression of CD64 on CD14++CD16- and CD14++CD16+ monocytes were positively correlated with erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPA) and disease activity score 28 (DAS28). Furthermore, the expression of CD64 on CD14++CD16+ monocytes was found to be associated with the serum level of IL-6. In conclusions, these data demonstrated the expression of CD64 on CD14++CD16- and CD14++CD16+ monocytes are elevated and associated with the disease activity in RA.