Fig. 1.

IFN-γ down-regulates CXCR-4 and CCR-5 expression by monocytic cells. (a) PBMCs (1 × 10⁶/ml) from 10 HIV-negative, six HIV-infected and 10 HIV-negative cord blood donors were incubated with IFN-γ (1 ng/ml) for 24 h, and the effects on cell surface CXCR-4 and CCR-5 expression by CD14⁺ monocytes were determined by flow cytometry. (b) PBMCs (1 × 10⁶/ml) from a representative HIV-negative individual were incubated with various concentrations of IFN-γ for 24 h followed by analysis of cell surface CXCR-4 and CCR-5 expression on CD14⁺ monocytes by flow cytometry. (c)Representative flow cytometry histograms of the effect of IFN-γ on the expression of CXCR-4 and CCR-5 by purified monocytes. CD14⁺ purified monocytes (2 × 10⁵/ml) isolated from a HIV-negative individual, an HIV-negative cord blood donor and an HIV-positive adult were stimulated with IFN-γ (1 ng/ml) for 24 h followed by determination of cell surface CXCR-4 and CCR-5 expression by CD14⁺ monocytes by flow cytometry. Shaded and unshaded histogram represent chemokine receptor expression in unstimulated and IFN-γ-stimulated cells, respectively.