Macrophage activation and programming and its role for macrophage function in glomerular inflammation

Macrophages have a central role in the control of inflammation because, depending on the local microenvironment, they can develop into cells that cause further injury or facilitate tissue repair. Understanding what signals determine whether macrophages develop into cells that promote injury or facilitate repair is one of the most important issues in inflammatory cell biology, not least because of the opportunities for developing novel therapies. This is highly relevant to glomerulonephritis because of the prominence of the macrophage infiltrate in all types of severe or progressive nephritis, and the present unsatisfactory nature of treatments for these diseases. This review will focuses on how macrophages are activated in vitro and in normal and inflamed glomeruli. The new concept of 'macrophage programming' is introduced and novel strategies to alter macrophage function within nephritic glomeruli that could be used for the treatment of glomerular inflammation are highlighted.