Factor friction: protective and pathogenic roles for complement factors in immune complex glomerulonephritis.

The classical pathway of complement is activated in patients with immune complex glomerulonephritis. However, Alexander et al. demonstrate that factor H, an alternative pathway regulator, is critical for protecting mice from immune-complex-mediated glomerular injury. In mice that lack factor H, signaling through the C5a receptor is necessary for the development of injury. These results suggest that factor H may be critical for limiting injury in a wide range of autoimmune and inflammatory renal diseases.