Significant increase of B7-H1 surface expression by IL-4 and TNF α treatment of RCC cell lines. Different RCC cell lines (Hal31RC, Hal161RC, MZ1790RC) were treated with either IL-4 or TNFα alone before B7-H expression was determined by flow cytometry as described in Materials and Methods at 72 hrs. A) Shown are FACS histogram overlay plots for B7-H1, B7-H2, B7-H3 and B7-H4. Each plot shows overlay graphs, depicting constitutive protein expression and expression upon single or combined cytokine treatment. Representative data of at least 3 different experiments are shown. B) Cytokine-mediated induction of B7-H1 and B7-H2 in % using constitutive expression levels as reference value. Combined data of 3 different experiments are given.