Immune system in renal injury and repair: Burning the candle from both ends?

This brief overview is focused on the inherent duality of immune responses: on the one hand they may induce inflammation and precipitate injury, on the other, a number of examples of participation in organ and tissue repair are growing. These processes will be reviewed from the nephrological stand-point. Specifically, the role of different leukocyte subsets, innate immunity, nitric oxide production, and stem cells, among others, are presented.