(A) Concentration-dependent increase of MIP-1 receptors on LP CD34⁺ in response to TNF-. Purified CD34⁺ cells were cultured for 24 hours in the absence or presence of varying concentrations of TNF-, as detailed in the legend of Fig 3. Thereafter, the expression of MIP-1 receptors on CD34⁺ cells was analyzed by flow cytometry. Bars represent the mean ± SEM of n independent experiments. (*) Denotes significant differences between the TNF-–treated cells and controls (P < .05). (B) IFN-γ–induced upregulation of MIP-1 receptors on LP CD34⁺ cells. Purified LP CD34⁺ cells were cultured for 24 hours in the absence or presence of IFN-γ (1,000 U/mL) as detailed in the legend of Fig 3. Thereafter the expression of MIP-1 receptors on CD34⁺cells was analyzed by flow cytometry. Bars represent the mean ± SEM of four independent experiments. (*) Denotes significant difference between the IFN-γ–treated cells and the control (P < .05).