Murine MIP-1γ or macrophage inflammatory protein (MlP)-related protein 2 (MRP-2) was isolated from a murine macrophage cell line, RAW 264.7. Mu MIP-1γ/MRP-2 is composed of 122 amino acids, of which the first 21 residues constitute a putative signal sequence. The putative mature protein is composed of 101 amino acids with a molecular weight of 11.600. Mu MIP-1γ/MRP-2 is structurally similar to Mu CIO and MlP-la. Mu MIP-1γ/MRP-2 mRNA was preferentially delected in monocytes and macrophage cell lines but not in T and В cells. A striking feature of this chemokine in terms of expression pattern is that the mRNA is ubiquitously found in all tissues and inflammation is not required for its expression. The Mu MIP-1γ/MRP-2 gene, termed Scyd9, was mapped to the central region of mouse chromosome 11 near Scyal and Scya2, which are members of the CC chemokine superfamily. Mu MIP-1γ/MRP-2 is a potent ligand for CCRl. Recombinant Mu MlP-ly/ MRP-2 significantly suppressed colony formation by mouse bone marrow, granulocyte-macrophage, ery-throid. and mullipolenlial progenitor cells stimulated by combinations of growth factors.