A complex comprising an HLA Class 1 molecule and attaching means for selectively attaching the HLA class 1 molecule to a target cell is disclosed, and a method is provided for producing or enhancing an immunological response against a target cell, by attaching said complex to the target cell. Where the target is a diseased, foreign or malignant cell, this method may be used to promote the lysis of the targeted cell by T cells in the immune system. Where the target cell is an antigen presenting cell, this method may be used to promote the proliferation of specific T cell clones. The invention is of potential use in the prevention and treatment of malignant diseases including cancer and leukemia, infectious diseases including viral infections such as HIV, bacterial infections including tuberculosis, and parasitic infections including malaria.