Immunohistochemistry for MHC class II (HLA-DR) (a) and the N-terminus of Foxp3 (b) in biliary tract cancers. In addition to infiltrating mononuclear cells, carcinoma cells are positive for HLA-DR ((a), arrows). The antibody reacting with the N-terminus of Foxp3 (b) highlights the nucleus and cytoplasm of cholangiocarcinoma cells.
