Chemokine that acts as a chemoattractant for monocytes, macrophages and dendritic cells, and which is involved in immune regulation and lymphocyte trafficking (PubMed:16455961, PubMed:23115081, PubMed:39293486, PubMed:40279398). Activates the C-X-C chemokine receptor GPR25 (PubMed:39293486, PubMed:40279398). Plays a key role in lymphocyte homing by activating the receptor GPR25 on lymphocytes, mediating lymphocyte recruitment into the respiratory, upper gastrointestinal, biliary and genito-urinary tracts (PubMed:39293486, PubMed:40279398). Plays a role in angiogenesis and possibly in the development of tumors (PubMed:16989774, PubMed:23115081). Acts as an anti-inflammatory in the stomach (PubMed:23115081). May play a role in the innate defense against infections (PubMed:17307946). {ECO:0000269|PubMed:16455961, ECO:0000269|PubMed:16989774, ECO:0000269|PubMed:17307946, ECO:0000269|PubMed:23115081, ECO:0000269|PubMed:39293486, ECO:0000269|PubMed:40279398}. [4-Cys CXCL17]: Seems to exhibit much higher chemoattractant potency on monocytes and macrophages than 6-Cys CXCL17. . This is the function of Ensembl gene identifier ENSG00000189377 (CXCL17, C-X-C motif chemokine ligand 17).