Highly cationic protein that has multiple functions. Acts as a 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 (PubMed:25351403). May regulate keratinocyte proliferation (PubMed:29872130). In addition, through activation of Mas-related G protein-coupled receptors (MRGPRs) contributes to pruritogenesis by activating itch-selective sensory neurons and mast cells degranulation (PubMed:35704588). {ECO:0000269|PubMed:25351403, ECO:0000269|PubMed:28900043, ECO:0000269|PubMed:28936214, ECO:0000269|PubMed:29872130, ECO:0000269|PubMed:35704588}. Has antimicrobial activity against Gram-positive bacteria, including Staphylococcus aureus and Actinomyces spec., and Mycoplasma hominis and lentivirus (PubMed:25585381). . This is the function of GPR15LG (G protein-coupled receptor 15 ligand, ENSG00000188373).