A recent study suggests that inhibiting the homing and proliferative signals of macrophages might slow cyst growth in polycystic kidney disease (PKD). Karihaloo et al. found that numbers of alternatively activated macrophages were abnormally high around cysts in orthologous mouse models of PKD. They found that proliferation of cyst-lining cells was reduced in macrophage-depleted mice compared with control mice, and that cystic index was lower, renal parenchyma were better preserved and renal function was improved.