Modulation of CXC Chemokine Receptor Expression and Function in Human Neutrophils during Aging In Vitro Suggests a Role in Their Clearance from Circulation
Figure 1
Expression of CXCR4, CXCR1, and CXCR2 in human granulocytes during aging in vitro.
(a) Surface expression of CXCR4 on human granulocytes freshly isolated (0 hours) and cultured at 37°C (1 hour–18 hours) is shown, as measured by flow cytometry. Fluorescence histograms of a representative experiment are shown. Neutrophils which were kept at 4°C to prevent aging served as an additional control
(b) CXCR4 expression on granulocytes cultured for 18 hours at 37°C in the presence of the stimulatory cytokines granulocyte colony-stimulating factor (G-CSF), interleukin-1 (IL-1β), tumor necrosis-factor (TNF-α), and interleukin-8 (IL-8). Fluorescence histograms of a representative experiment are shown. The correponding control without cytokines is shown in Figure 1(a) (37°C 18 hours)
(c) Surface expression of the IL-8 receptors CXCR1 and CXCR2 on freshly isolated and cultured (37°C, 18 hours) human granulocytes. Fluorescence histograms of a representative experiment are shown
(d) Quantitative analysis (mean fluorescence, ) of the chemokine receptor expression in repeated experiments according to the representative examples shown in (a)–(c). The differences in CXCR4 and CXCR2 expression were statistically significant (***, 0 hours versus 18 hours). Control: Isotype control, 0 hours
(e) Expression of CXCR4 mRNA in freshly isolated (0 hours), aged (18 hours, 37°C) PMN and cells kept at 4°C to prevent senescence, as analyzed by Northern blot of total RNA. Positive control: mononuclear cells (PBMNCs) and HL-60. Negative control: KG1a. β-actin was used as an internal standard and control for equal mRNA loading
