Figure 3 Analysis of cell surface IFNγR1 and STAT1 phosphorylation in response to IFNγ stimulation. (A) Peripheral blood mononuclear cells were cultured with RPMI 1640 containing 15% FCS, 50 μg/l LPS and 100 μg/l M‐CSF for 48 hours. The cells were stained with phycoerythrin (PE)‐conjugated anti‐interferon γ receptor 1 (IFNγR1) antibody and fluorescein isothiocyanate (FITC)‐conjugated anti‐CD14 antibody and analysed by flow cytometry. The data represent the levels of expression of IFNγR1 on CD14‐positive cells. Bold line, patient; solid line, control. The dotted line indicates binding of the appropriate isotype control antibody. (B) Peripheral blood mononuclear leukocytes were incubated in RPMI 1640 that was supplemented with 15% fetal calf serum (FCS), 100 μg/l macrophage colony‐stimulating factor (M‐CSF), and 20 μg/l lipopolysaccharide (LPS) for 48 hours. The harvested cells were washed and then cultured for an additional 18 hours in RPMI 1640 medium alone. Then cells were treated with or without 50 μg/l LPS and 10 000 U/ml IFNγ for 30 minutes, and the cells were then stained with anti‐STAT1 (pY701) antibody and analysed by flow cytometry. Bold line, patient sample with cytokine stimulation; solid line, normal subject sample with cytokine stimulation; dotted line, normal subject sample without cytokine stimulation.