Open Access Research article

Induction of tumour necrosis factor receptor-expressing macrophages by interleukin-10 and macrophage colony-stimulating factor in rheumatoid arthritis

Koji Takasugi1, Masahiro Yamamura2*, Mitsuhiro Iwahashi1, Fumio Otsuka1, Jiro Yamana1, Katsue Sunahori1, Masanori Kawashima1, Masao Yamada3 and Hirofumi Makino1

Author Affiliations

1 Department of Medicine and Clinical Science, Graduate School of Medicine, Dentistry, Pharmaceutical Sciences, Okayama University, 2-5-1 Shikata-cho, Okayama 700-8558, Japan

2 Department of Rheumatology, School of Medicine, Aichi Medical University, Nagakute-cho, Aichi 480-1195, Japan

3 Department of Virology, Graduate School of Medicine, Dentistry, Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama 700-8558, Japan

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Arthritis Research & Therapy 2006, 8:R126  doi:10.1186/ar2015

Published: 19 July 2006

Abstract

Despite its potent ability to inhibit proinflammatory cytokine synthesis, interleukin (IL)-10 has a marginal clinical effect in rheumatoid arthritis (RA) patients. Recent evidence suggests that IL-10 induces monocyte/macrophage maturation in cooperation with macrophage-colony stimulating factor (M-CSF). In the present study, we found that the inducible subunit of the IL-10 receptor (IL-10R), type 1 IL-10R (IL-10R1), was expressed at higher levels on monocytes in RA than in healthy controls, in association with disease activity, while their expression of both type 1 and 2 tumour necrosis factor receptors (TNFR1/2) was not increased. The expression of IL-10R1 but not IL-10R2 was augmented on monocytes cultured in the presence of RA synovial tissue (ST) cell culture supernatants. Cell surface expression of TNFR1/2 expression on monocytes was induced by IL-10, and more efficiently in combination with M-CSF. Two-color immunofluorescence labeling of RA ST samples showed an intensive coexpression of IL-10R1, TNFR1/2, and M-CSF receptor in CD68+ lining macrophages. Adhered monocytes, after 3-day preincubation with IL-10 and M-CSF, could produce more IL-1β and IL-6 in response to TNF-α in the presence of dibutyryl cAMP, as compared with the cells preincubated with or without IL-10 or M-CSF alone. Microarray analysis of gene expression revealed that IL-10 activated various genes essential for macrophage functions, including other members of the TNFR superfamily, receptors for chemokines and growth factors, Toll-like receptors, and TNFR-associated signaling molecules. These results suggest that IL-10 may contribute to the inflammatory process by facilitating monocyte differentiation into TNF-α-responsive macrophages in the presence of M-CSF in RA.