We have designed several complete devices in order to display multiple proteins on the membrane of mammalian cells using a single system. Our favorite composite part is TRE-Tri_display-hGH (<a href="http://parts.igem.org/wiki/index.php?title=Part:BBa_K2520007">BBa_K2520007</a>). This composite part consists of the TRE promoter, our novel Tri-Display system and the hGH terminator. The Tri-Display is a modular display vector capable of displaying up to three different proteins on the membrane of mammalian cells in equimolar ratios. The Tri-Display contains three display segments connected by P2A (cleavage sites). Each display component consists of an Igk leader (signal peptide), a protein tag (for easy detection), a protein flanked by unique restriction enzymes (for easy exchange of the displayed protein) and a PDGFR (anchors proteins to the membrane). The proteins that we chose to express on the membrane are three different epitopes related to a specific disease (this part has specific epitopes that are known targets of multiple sclerosis). The addition of the TRE promoter allows inducible expression contingent upon the presence of doxycycline and a chosen activator protein (Tta or rTta).