Fig. 7. Lack of Ii diminishes the efficiency of cytosolic antigen presentation on MHC class II. (A-C) Macrophage APCs from wild-type or Ii^-/- H-2^b mice were loaded with the antigen using the loading pathway indicated. These were tested in titrating concentrations for their ability to stimulate the T cell line identified in each panel. B3 recognizes an OVA peptide in the context of the class I molecule, H-2K^b, whereas 13.8 recognizes an OVA peptide in the context of the class II molecule, I-A^b.