Projects

1. Differentiation potential and pathways of monocytes in normal and inflamed joints

Bone marrow derived mononuclear cells form two important cellular components of the synovial lining of joints. These are specialised macrophages (type A synoviocytes) that line the synovium and dendritic cells (DC) that are present in the synovial membrane. There is little precise information about the origins of these cells, although it is known that macrophages arise from blood monocytes, while in vitro studies indicate that monocytes are precursors of DC under some circumstances. Nevertheless, there may also be specific circulating DC precursors and recent evidence suggests that monocytes consist of at least two subsets, with different differentiation potentials. We wish to know the potential of blood monocytes, and monocyte subsets, to differentiate into macrophages and/or DC, and some of the factors that decide which differentiation pathways are taken by these cells.

We have developed a CD45 congenic of the arthritis prone DA rat strain, allowing us to trace the fate of genetically marked donor cells in wild-type recipients. Recent studies by a visiting student have shown that after adoptive transfer to rats with established arthritis, blood monocytes of donor origin can be detected in the synovial tissues of the recipients and that these cells express new surface markers. Furthermore, during the development of arthritis, circulating monocytes exhibit changed surface antigen phenotype. These preliminary observations form an excellent foundation for more detailed investigations into the production of monocytes during the establishment of an autoimmune disease, the responses of the monocytes to circulating mediators of inflammation, and the factors that are responsible for the further differentiation of monocytes in tissues affected by T cell-mediated inflammation. The project is well suited for Honours, because the system and methods are established and there is ample opportunity to design challenging experiments and produce novel and important data. Techniques involved will include induction and assessment of arthritis in animals, preparation and purification of blood moncytes, use of immunomagnetic beads and/or FACS to purify subsets of monocytes, collection of cells from tissues by enzymatic techniques, multi-fluorochrome analysis of cell surface antigens, immunohistochemistry on cell smears and tissue sections and in vitro assay of functional activity of APCs.

Funding Sources

NH&MRC: “The immunological microenvironment in the synovium during experimental polyarthritis in the rat”.