Exhibits antimicrobial activity against Gram-negative bacteria and Gram-positive bacteria, with highest activity against Gram-negative bacteria (PubMed:10837369, PubMed:9202117). Antimicrobial activity against P.aeruginosa seems to be salt-sensitive and is reduced with high salt concentrations greater than 25 mM (PubMed:10837369). Also exhibits antimicrobial activity against the yeast C.albicans (PubMed:10837369, PubMed:30050988, PubMed:9202117). Permeabilizes C.albicans cell membranes via targeting plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2), thereby leading to cell fragmentation and cell death (PubMed:30050988). Acts as a ligand for C- C chemokine receptor CCR6 (PubMed:10521347, PubMed:20068036). Binds to CCR6 and induces chemotactic activity of CCR6-expressing cells, such as immature dendritic cells and memory T cells (PubMed:10521347, PubMed:20068036). {ECO:0000269|PubMed:10521347, ECO:0000269|PubMed:10837369, ECO:0000269|PubMed:20068036, ECO:0000269|PubMed:30050988, ECO:0000269|PubMed:9202117}. This is the function of ENSG00000177257 (DEFB4B, defensin beta 4B).