This invention describes the production and properties of a pMHC Multiplexer. The pMHC Multiplexer is a spatially limited composition of two different molecules, an encoding molecule (i.e. an RNA or DNA molecule), and an encoded peptide, where said encoded peptide is encoded by said encoding molecule. Furthermore, the peptide is complexed to a MHC complex and thus is part of a pMHC complex. A preferred embodiment of the invention describes the production and properties of an example pMHC Multiplexer that is a phage particle carrying on its surface a number of identical pMHC complexes, where the peptide of the pMHC complexes is encoded by the DNA contained within the phage particle, and where a covalent or non-covalent bond links a phage coat protein with a pMHC complex and/or a pMHC Multimer. Another preferred embodiment of the invention describes the production and properties of an example pMHC Multiplexer that is a eukaryotic cell carrying on its surface a number of identical pMHC complexes, where the peptide of the pMHC complexes is encoded by the DNA contained within the cell. Yet another preferred embodiment of the invention describes the production and properties of an example pMHC Multiplexer where the encoding molecule is a DNA or RNA, and where the binding of pMHC Multiplexer to T cell receptor (TCR) can be detected by PCR-based analysis. Yet another preferred embodiment of the invention describes the production and properties of an example pMHC Multiplexer that comprises one or more identical pMHC complexes, where the encoding molecule is directly linked to at least one peptide (p) of one of the pMHC complexes, and thus, the peptide (p) of the pMHC complex(es) is encoded by said encoding molecule directly linked to it.