Schematic diagram illustrating the probable mechanism of induction of CTL effector function by anti-tumor-associated antigen Fab-HLA-A2/Flu conjugates oligomerized on the surface of tumor target cells. Note that the free conjugates should not bind to T cell receptor (TCR) due to the low affinity of the monomeric MHC/peptide complex-TCR interaction. The unique advantage of the conjugates is that their antibody site (in red) can associate with highly expressed, non-MHC restricted, tumor-associated antigens, while their MHC/peptide site (in blue and yellow), when coated at high density on the target cell surface, can induce the binding and effector function of specific cytotoxic T lymphocytes. Thus, the Fab-MHC/peptide conjugates do make a functional bridge between antibody and T cell recognition of tumor cells.