ACKR1 and HIV infectious disease: The median frequency of neutrophils exhibiting proteolytic activity was still higher in DARC-null compared to DARC-positive individuals at 120 min post bead incubation (74.5 vs. 64.3% in HIV uninfected and 67.9 vs. 55.4% in HIV infection in DARC-null and DARC-positive individuals, respectively).