Rapid selection procedures. Left: Selection of virus-specific cytotoxic T cells recognizing an HLA-restricted peptide by incubation with an HLA–peptide multimer and then a collection of multimer positive T-cells. Right: Selection by the gamma capture. Donor cells are stimulated with antigen and activated cells that secrete IFN-γ are selected using an immunomagnetic separation device that captures the IFN-γ–secreting T cells specific for the virus.