Chemotactic factor that mediates lymphocytes recruitment to epithelia through binding and activation of the G-protein coupled receptor GPR15 (PubMed:28900043,PubMed:28936214). May be a tumor suppressor; together with SUSD2 has a growth inhibitory effect on colon cancer cells which includes G1 cell cycle arrest (By similarity). Has antimicrobial activity against Gram-positive bacteria, including Staphylococcus aureus and Actinomyces spec., and Mycoplasma hominis and lentivirus. Interacts with SUSD2; the interaction is direct. Highly abundant in the testis, colon, eye, and tongue. Detected in the epithelial layer of the colon, but not the small intestine. Up-regulated by Imiquimod in the skin (PubMed:28900043).