Macrophages induce proliferation of cystic epithelial cells in the Cys1cpk and Pkd1 models [37, 38] and their markers are abundantly expressed in kidneys from ARPKD patients [15, 39, 40] as well as Cys1cpk/cpk mice carrying the CAST-derived Kif12 allele [8, 15, 39]. This evidence concerns the gene CAST and autosomal recessive polycystic kidney disease.