Chemokine (C-C motif) ligand 23 (CCL23) is a small cytokine belonging to the CC chemokine family that is also known as Macrophage inflammatory protein 3 (MIP-3) and Myeloid progenitor inhibitory factor 1 (MPIF-1). CCL23 is predominantly expressed in lung and liver tissue, but is also found in bone marrow and placenta.[1] It is also expressed in some cell lines of myeloid origin. CCL23 is highly chemotactic for resting T cells and monocytes and slightly chemotactic for neutrophils. It has also been attributed to an inhibitory activity on hematopoietic progenitor cells.[1] The gene for CCL23 is located on human chromosome 17 in a locus containing several other CC chemokines. CCL23 is a ligand for the chemokine receptor CCR1.[2]