Natural Killer Cells: Role in the pathogenesis of rheumatoid arthritis major contributors or essential homeostatic modu

Rheumatoid arthritis is a global health problem caused by chronic inflammation in affected joints. Our group identified that a protein called Tumour Necrosis Factor (TNF) was central to the destructive processes in the disease rheumatoid arthritis. These observations led to the development of new drugs, which block the action of TNF, and were demonstrated to be extremely effective in RA patients. These anti-TNF drugs have now been used successfully in over 1,000,000 patients worldwide. Whilst this therapy is effective, it is not a cure and we are continuing to investigate other targets in this disease which will lead to treatments which are even more effective and safer for the patients. The chronic inflammation in RA has been demonstrated to be due to persistent production of TNF in the diseased joint which is dependent on a subset of T cells. Recently we have described how surrogates for these rheumatoid arthritis T cells can be generated using T lymphocytes from normal peripheral blood stimulated in culture with a cocktail of cytokines that are present within the rheumatic joint. We also found that within the T cell population there is a large number of natural killer cells that demonstrate pathogenic properties towards cells of bone; a tissue destroyed in RA joints. In this proposal we wish to translate our current knowledge and understanding of NK cells into an in vivo model of rheumatoid arthritis. We anticipate that the study will lead to a better understanding of the mechanisms involved in driving chronic inflammation in rheumatoid arthritis and identify new novel targets for therapeutic intervention.

Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects more than 1% of the world population. Although anti-TNF drugs are the most successful therapy to date, only 70% of patients benefit from this treatment. Therefore, it is imperative we have better understanding of the mechanisms underlying the establishment of chronic inflammation. Whilst the role of cytokines (particularly TNF) in contributing to the pathogenesis of RA has been well documented, the role of T lymphocytes has remained unclear, and the involvement of NK cells not fully understood. NK cells are interesting candidates for therapy since despite their low frequency they are the ?main producers? of interferon gamma at inflammatory sites. Our group has recently shown that surrogates for RA synovial T cells can be generated ex vivo using T lymphocytes from normal peripheral blood stimulated in culture with a cocktail of cytokines (TNF, IL-6 and IL-2). Within this lymphocyte population there is a significant expansion of activated NK cells which, when sorted, are potent effectors of contact-mediated activation of monocytes, macrophages and osteoclasts. In this proposal we wish to translate our current (and limited) knowledge and understanding of cytokine-activated NK cells into the RA-SCID in vivo model of rheumatoid arthritis. We believe this model will allow us to dissect the potential of NK cells to contribute to inflammatory events both in synovial tissue and bone, but also to address their potential not only as inducers of inflammation but also as homeostatic regulators. The RA-SCID model is based upon the engraftment of human synovial tissue (from RA patients undergoing surgery) subcutaneously onto the backs of SCID/beige mice where the human transplant tissue remains viable, becomes vascularised and develops a connection with the mouse vasculature. In addition we will also engraft biopsy fragments of femoral bone to address the potential of NK cells to support osteoblast differentiation and activity as well as NK cell effects on osteoclastogenesis in vivo. Migration of cytokine-activated NK cells to synovial tissue and bone in vivo will be assessed by transfer of labelled cells 4 weeks after transplantation and enumeration of migration of the injected cells to the transplanted tissue using imaging techniques, and removal of biopsies with ex vivo enumeration. This proposal will address (for the first time) the potential of NK cells both to contribute to inflammation but also regulate inflammatory events in an in vivo model relevant to human RA disease.