Chemokines are a family of small chemotactic cytokines, or proteins secreted by cells. Chemokines share the same structure similarities such as small size, and the presence of four cysteine residues in conserved locations in order to form their 3-dimensional shape. Some of the chemokines are considered pro-inflammatory which can be induced to recruit cells of the immune system to a site of infection during an immune response, while others are considered homeostatic and are implied in controlling the migration of cells during normal processes of tissue maintenance and development. There are four members of the chemokine family: C-C kemokines, C kemokines, CXC kemokines and CX3C kemokines. The C-C kemokines have two cysteines nearby the amino terminus. There have been at least 27 distinct members of this subgroup reported for mammals, called C-C chemokine ligands-1 to 28. Chemokine ligand 7(CCL7), also known as MCP-3, is a isform of the C-C chemokine subfamily of the chemokine family which is produced by certain tumor cells and by macrophages. It also own two adjacent N-terminal cysteine residues. Chemokine ligand 7(CCL7) spacifically attracts monocytes, and regulates macrophage function.

> 90 % as determined by SDS-PAGE.