Interestingly, CKIP-1 inhibits macrophage proliferation specifically at the late stage after M-CSF stimulation in cultured cells and Ckip-1−/− mice spontaneously develop a macrophage-dominated splenomegaly and myeloproliferation11, indicating a role of CKIP-1 in macrophage regulation. This evidence concerns the gene PLEKHO1 and Splenomegaly.