Receptor for a number of inflammatory CC-chemokines including CCL3/MIP-1-alpha, CCL4/MIP-1-beta and RANTES and subsequently transduces a signal by increasing the intracellular calcium ion level. May play a role in the control of granulocytic lineage proliferation or differentiation. Participates in T-lymphocyte migration to the infection site by acting as a chemotactic receptor (PubMed:30713770). {ECO:0000269|PubMed:10383387, ECO:0000269|PubMed:11323418, ECO:0000269|PubMed:30713770, ECO:0000269|PubMed:8639485, ECO:0000269|PubMed:8663314, ECO:0000269|PubMed:8699119}. (Microbial infection) Acts as a coreceptor (CD4 being the primary receptor) of human immunodeficiency virus-1/HIV-1. {ECO:0000269|PubMed:10383387, ECO:0000269|PubMed:21763489, ECO:0000269|PubMed:8649511, ECO:0000269|PubMed:8649512, ECO:0000269|PubMed:9632396}. This is the function of CCR5 (C-C motif chemokine receptor 5, ENSG00000160791).