Expression and gene regulation of B7-H1 and B7-DC. (A) Reverse transcription–polymerase chain reaction (RT-PCR) of human lymphoid cell lines for B7-H1 and B7-DC expression. β-Actin is shown as a cDNA control. (B) Histograms showing B7-H1 and B7-DC expression levels in human lymphoid cell lines. Open histograms represent isotype controls. (C) Luciferase reporter assay detecting alterations in B7-H1 and B7-DC promoter activities by EBV latent membrane proteins. Either flag-tagged LMP1, LMP2A expression vector, or mock vector was transfected with one of the reporter vectors into 293T cells. LMP1 and LMP2A protein expression was confirmed by Western blotting (left). Schematic diagrams of promoter regions of B7-H1 and B7-DC cloned into the pGL3-enhancer vector are shown (right). Numbers are the nucleotide positions that refer to the 5′ boundary of exon 1 of each gene, and binding sites of representative transcription factors are indicated. Luciferase activities are expressed relative to the activity of the mock vector–transfected controls. Values are the means of 3 independent experiments; bars represent SD. (D) Immunohistochemical analysis of 4 HL tissue specimens. HE (i) and LMP1 staining (ii) (original magnification ×400); HE (iii), CD3 (iv), CD30 (v), B7-H1 (vi), and B7-DC (vii) (original magnification ×1000), focusing on H/RS cells and surrounding T cells. EBV is shown to be positive in the top 2 samples and negative in the bottom 2.