Monocyte surface expression of Fcγ receptor RI (CD64), a biomarker reflecting type-I interferon levels in systemic lupus erythematosus

• Published in: Arthritis research & therapy 2010-01, Vol.12 (3), p.R90-R90, Article R90
• Main Authors: Li, Yi, Lee, Pui Y, Kellner, Erinn S, Paulus, Matthew, Switanek, Juliana, Xu, Yuan, Zhuang, Haoyang, Sobel, Eric S, Segal, Mark S, Satoh, Minoru, Reeves, Westley H
• Format: Article
• Language: English
• ISSN: 1478-6354; 1478-6354; 1478-6362
• DOI: 10.1186/ar3017

Introduction More than half of systemic lupus erythematosus (SLE) patients show evidence of excess type I Interferon (IFN-I) production, a phenotype associated with renal disease and certain autoantibodles. However, detection of IFN-I proteins in serum is unreliable, and the measurement of interferon-stimulated gene (ISG) expression is expensive and time consuming. The aim of this study was to identify a surrogate marker for IFN-I activity in clinical samples for monitoring disease activity and response to therapy. Methods Monocyte surface expression of Fe gamma receptors (Fc gamma Rs), chemokine receptors, and activation markers were analyzed with flow cytometry in whole blood from patients with SLE and healthy controls. Fc gamma R expression also was measured in peripheral blood mononudear cells (PBMCs) from healthy controls cultured with Toll-like receptor (TLR) agonists, cytokines, or serum from SLE patients. Expression of ISGs was analyzed with real-time PCR. Results Circulating CD14 super(+) monocytes from SLE patients showed increased surface expression of Fc gamma RI (CD64). The mean fluorescent intensity of CD64 staining correlated highly with the ISG expression (MX1, IFI44, and Ly6E). In vitro, IFN-I as well as TLR7 and TLR9 agonists, induced CD64 expression on monocytes from healthy controls. Exposure of monocytes from healthy controls to SLE sera also upregulated the expression of CD64 in an IFN-I-dependent manner. Decreased CD64 expression was observed concomitant with the reduction of ISG expression after high-dose corticosterold therapy. Conclusions Expression of CD64 on circulating monocytes is IFN-I Indudble and highly correlated with ISG expression. Flow-cytometry analysis of CD64 expression on circulating monocytes is a convenient and rapid approach for estimating IFN-I levels in SLE patients.