Flow cytometrical detection of IFN-γ–mediated increased transient calcium flux response to RANTES in cells derived from elutriated monocytes from a healthy, HIV-seronegative donor. Untreated cells (depicted in the left panel) were compared with IFN-γ pretreated cells (right panel) in their response to 50 ng/mL RANTES (R&D Systems Inc). Fluorescence of bound versus unbound intracellular calcium in response to the chemokine was detected 5 days after treatment. The pattern of response is representative for analysis of monocytes derived from 6 subjects.