A DNA sequence encoding the extracellular domain (Met1-Ala105) of human CD3D (P04234) was fused with a flag tag at the C-terminus, constructed the plasmid 1; A DNA sequence encoding the extracellular domain (Met1-Asp126) of human CD3E (P07766) was fused with a polyhistidine tag at the C-terminus, constructed the plasmid 2. The two plasmids were co-expressed and the human CD3D/CD3E heterodimer was purified. Purity (43.8+13.1+41.9) % as determined by SDS-PAGE