Mononuclear phagocyte system in kidney disease and repair

The mononuclear phagocyte system is comprised of circulating monocytes, tissue macrophages and dendritic cells (DCs) that play key roles in tissue homeostasis, immune surveillance, and immune and non-immune-mediated tissue injury and repair. This review summarizes the various subsets within this system that exhibit significant functional and phenotypic diversity that can adapt to their surrounding microenvironments during inflammation and in response to colony-stimulating factor (CSF)-1. The current understanding of the co-ordination of monocyte infiltration into the homeostatic and diseased kidney through adhesion molecules, chemokines and chemokine receptors, and cytokines are described. Furthermore, the significant confusion and controversy associated with monocyte differentiation into renal macrophages and DCs following infiltration into the kidney, the considerable functional and phenotypic overlap between both tissue populations and their respective roles in immune and non-immune-mediated renal is also discussed. Understanding the factors that control the activation and recruitment of cells from the mononuclear phagocyte system during renal injury may offer an avenue for the development of new cellular and growth factor-based therapies in combination with existing therapies as an alternative treatment option for patients with renal disease.