This gene is one of several cytokine genes clustered on the q-arm of chromosome 17. Cytokines are a family of secreted proteins involved in immunoregulatory and inflammatory processes. This protein binds to several chemokine receptors including chemokine binding protein 2 and chemokine (C-C motif) receptor 5 (CCR5). CCR5 is a co-receptor for HIV, and binding of this protein to CCR5 inhibits HIV entry. The copy number of this gene varies among individuals; most individuals have 1-6 copies in the diploid genome, although rare individuals have zero or more than six copies. The human genome reference assembly contains two full copies of the gene (CCL3L3 and CCL3L1) and a partial pseudogene. This record represents the more telomeric full-length gene.