Abstract: A method for detecting T cells includes a first step of bringing a plurality of different antigenic peptides into contact with peptide-free MHC molecules which are arranged in an immobilized manner on a substrate in an array so that the plurality of different antigenic peptides bind to the peptide-free MHC molecules so as to form peptide-loaded MHC molecules, a second step of bringing a sample comprising the T cells into contact with the peptide-loaded MHC molecules on the substrate, and a third step of detecting the binding of the T cells to the peptide-loaded MHC molecules on the substrate.