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Open Access Research article

Recruitment of dendritic cells and macrophages during T cell-mediated synovial inflammation

Mahin Moghaddami1, Leslie G Cleland12, Gorjana Radisic3 and Graham Mayrhofer13*

Author Affiliations

1 Arthritis Research Laboratory, Hanson Research Institute, Institute of Medical and Veterinary Science, Frome Road, Adelaide, South Australia, 5000, Australia

2 Rheumatology Unit, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia, 5000, Australia

3 Discipline of Microbiology and Immunology, School of Molecular and Biomedical Science, University of Adelaide, North Terrace, Adelaide, South Australia, 5005, Australia

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Arthritis Research & Therapy 2007, 9:R120  doi:10.1186/ar2328

Published: 20 November 2007

Abstract

Adoptive transfer of adjuvant-induced arthritis was used in this study to examine local macrophages and dendritic cells (DCs) during T cell-mediated synovial inflammation. We studied the influx of CD11b+CD11c+ putative myeloid DCs and other non-lymphoid CD45+ cells into synovium-rich tissues (SRTs) of the affected hind paws in response to a pulse of autoreactive thoracic duct cells. Cells were prepared from the SRTs using a collagenase perfusion-digestion technique, thus allowing enumeration and phenotypic analysis by flow cytometry. Numbers of CD45+ cells increased during the first 6 days, with increases in CD45+MHC (major histocompatibility complex) II+ monocyte-like cells from as early as day 3 after transfer. In contrast, typical MHC II- monocytes, mainly of the CD4- subset, did not increase until 12 to 14 days after cell transfer, coinciding with the main influx of polymorphonuclear cells. By day 14, CD45+MHC IIhi cells constituted approximately half of all CD45+ cells in SRT. Most of the MHC IIhi cells expressed CD11c and CD11b and represented putative myeloid DCs, whereas only approximately 20% were CD163+ macrophages. Less than 5% of the MHC IIhi cells in inflamed SRT were CD11b-, setting a maximum for any influx of plasmacytoid DCs. Of the putative myeloid DCs, a third expressed CD4 and both the CD4+ and the CD4- subsets expressed the co-stimulatory molecule CD172a. Early accumulation of MHC IIhiCD11c+ monocyte-like cells during the early phase of T cell-mediated inflammation, relative to typical MHC II- blood monocytes, suggests that recruited monocytes differentiate rapidly toward the DC lineage at this stage in the disease process. However, it is possible also that the MHC IIhiCD11c+ cells originate from a specific subset of DC-like circulating mononuclear cells.