Myeloid progenitor inhibitory factor 1 (MPIF-1), also known as Chemokine (C-C motif) ligand 23 (CCL23) is a small cytokine belonging to the CC chemokine family. MPIF-1 is predominantly expressed in lung and liver tissue, but is also found in bone marrow and placenta. It is also expressed in some cell lines of myeloid origin. It is highly chemotactic for resting T cells and monocytes and slightly chemotactic for neutrophils. MPIF-1 has been shown to inhibit colony formation of bone marrow myeloid immature progenitors. It has also been attributed to an inhibitory activity on hematopoietic progenitor cells. MPIF-1 is a ligand for the chemokine receptor CCR1. 
Recombinant human MPIF-1/CCL23 (aa46-120)  produced in CHO cells is a single polypeptide chain containing 75 amino acids. A fully biologically active molecule, rhMPIF-1/CCL23 (aa46-120) has a molecular mass of 11.3 kDa analyzed by reducing SDS-PAGE and is obtained by chromatographic techniques at ExCell Bio.