Fig. 9. TAP transporter is not required for cytosolic antigen presentation on MHC class II. (A-C) Responses of the (A) OVA-specific MHC class I-restricted T cell line, B3Z, and (B,C) the E-specific MHC class II-restricted T cell line, 1H3.1. APCs used were either wild-type or TAP-1^-/- H-2b macrophages as indicated. Antigens indicated were loaded either cytosolically or exogenously and used to stimulate the relevant T cell lines in titrating numbers. IL2-secretion was monitored by ELISA as indicated in the text. (D) Macrophage APCs from TAP-1^-/- mice were loaded cytosolically with GST-E_52-68-myc and stained with the Y-Ae and anti-LAMP-1 antibodies. Image on the right shows overlay; green, Y-Ae; red, anti-LAMP-1. Scale bar, 10 µm. (E) Bone marrow-derived macrophages from TAP-1^-/- and wild-type mice were transiently transfected with E_52-68-eGFP or eGFP and stained for E-specific MHCII complexes with Y-Ae antibodies and detected by flow cytometry. Thin lined curve shows the signal from TAP-1^-/-, thick lined curve from wild-type cells and shaded area represent isotype control signals for Y-Ae antibody staining.