Complement: an unfinished symphony.

THE AUTHORS [Weiss et al. (10)] addressed the role of complement in hypertensive mice infused with ANG II and with NaCl in the drinking water. The complement focus was on C5aR1 cells that also expressed green fluorescent protein (GFP). The authors found GFP cells in interstitial areas of both heart and kidneys. These infiltrating cells were CD45 , indicating their origin from the bone marrow. Quite unexpectedly, where C5a receptor (C5aR)1 knockout mice were used, renal damage (quantitated by albuminuria) was reduced, but cardiac buildup of interstitial collagen type I, determined by histochemical staining and biochemical quantitation of collagen type I, was intensified. These data suggested that C5aR1 cells amplified renal damage but constrained collagen buildup in the heart in hypertensive mice.