A complex including an HLA class I molecule and attaching means for selectively attaching the HLA class I molecule to a target 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 cell is diseased, foreign, or malignant cell, this method may be used to promote lysis of the target cell by T cells in the immune system. Where the target cell is an antigen presenting cell, this method may be used to promote proliferation of specific T cell clones. Uses include prevention and treatment of diseases including cancer, leukaemia, infectious diseases, viral infections, such as HIV, bacterial infections, such as tuberculosis, and parasitic infections such as malaria.