Background Inflammatory process in bone marrow (BM) observed on MRI scans of rheumatoid arthritis (RA) patients (called bone marrow oedema) together with autoantibodies production was shown to proceed joint destruction in RA. Our previous studies supported the concept that BM actively participate in the pathogenesis of RA by TLR triggered B cell activity (1) and increased number of activated T cells (2).
Objectives In the present study we investigated IL-17 producers in BM.
Methods BM and peripheral blood (PB) samples were obtained from RA and osteoarthritis (OA) patients during total hip replacement surgery. Levels of IL-17AF, IL-17FF, IL-17AA, GMCSF and IL-21 in bone marrow plasma were determined by specific ELISA. Th1/Th2/Th17 proportions were evaluated by flow cytometry. To confirm production of IL-17 in BM immunohistochemistry examination was done. Comparison between the groups of patients were analysed by two-tailed Mann-Whitney U test.
Results We observed increased level of IL-17AF (147±104 pg/ml vs 115±74pg/ml, p<0,05) in bone marrow plasma from RA in comparison to OA. In contrast similar levels of IL-17FF were detected in RA BM (94± 115pg/ml) and OA BM plasma (44±66pg/ml). IL-17AA was not detected. Concentrations of both IL-17AF and IL-17FF were higher in BM than in PB. Surprisingly there were no differences between RA BM and OA BM levels of Th-17 related cytokines such IL-21 and GMCSF. We did not observe any statistically significant differences in percentage of IL-17, IFNγ or IL-4 producing lymphocytes in RA BM and OA BM. Immunohistological staining confirmed higher expression of IL-17 in RA BM in comparison to OA BM. We also observed strong IL-17 staining in granulocytes.
Conclusions IL-17AF is overproduced in RA bone marrow. There are two main sources of these cytokine in RA BM: T cells and granulocytes
W Rudnicka et al.: Eur J Immunol 2009; 1211–20
E Kuca-warnawin et al.: Ann Rheum Dis 2011;227–33
Acknowledgement This work was sponsored by by grant No UMO-2011/03/B/NZ6/05035 from National Science Centre
Disclosure of Interest None declared