CCL28 (CC chemokine ligand 28) is a novel CC chemokine identified by TBLASTN searches of the Human Genome Systems (HGS) and Genbank dbEst database using a human chemokine consensus sequence. Human CCL28 cDNA encodes a 127 amino acid (aa) residue precursor protein with a putative 22 aa residue signal peptide that is cleaved to produce the 105 aa residue mature protein. Human and mouse CCL28 are highly conserved, sharing 83% aa identity in their mature regions. Among CC chemokines, CCL28 shares the most homology with CCL27/CTACK. The mouse CCL28 gene has been mapped to the distal region of chromosome 13. Human and mouse CCL28 RNA expression was found to be highest in normal and pathologic colon with the protein being expressed by epithelial cells. Human CCL28 RNA was also present in normal and asthmatic lung tissues. The receptor for CCL28 has been identified as the CCR10 (GPR2 orphan receptor) which is also the receptor for CCL27/CTACK.