Figure 5.

Characterization of Tupaia CD81. (a) CD81 expression in human hepatoma cells and in Tupaia and rat hepatocytes. Cells (5 × 10⁵) grown in monolayer culture were lysed, and lysates were subjected to SDS-PAGE and immunoblot using a mouse monoclonal anti–human CD81 antibody (1D6), as described in Methods. CD81 protein is indicated on the right. Molecular masses (in kDa) are indicated on the left. (b) Analysis of CD81 expressed on the surface of freshly isolated Tupaia hepatocytes. Tupaia hepatocytes (10⁶ cells) were incubated with anti-CD81 or isotype control antibody (10 μg/ml). Staining and flow cytometry were performed as described in Methods. X axis and y axis show mean fluorescence intensity and relative number of stained cells, respectively. (c) Alignment of amino acid sequences of human, chimpanzee, Tupaia, tamarin, African green monkey, and rat LEL domain of CD81. Tupaia CD81-LEL cDNA was cloned and sequenced as described in Methods. CD81-LEL amino acid sequences of other species are depicted according to previous reports (11, 48).