Bioluminescent enumeration of surface antigen-specific cells using the streptavidin–luciferase fusion protein

To provide a convenient hemodiagnosis method distinguishing individual cell types, we used a streptavidin–luciferase fusion protein to enumerate cells expressing specific surface antigens by bioluminescence. The streptavidin–luciferase fusion protein, which possesses bioluminescent activity, forms a complex with a biotinylated antibody that is specifically attached to the target cell surface through direct recognition of the antibody ligand. When a suitable antibody was used to a stain, a model hemocyte mixture consisting of THP-1 and MOLT-3 cells, the measured bioluminescence resulting from specific binding of the immobilized antibody was proportional to the number of target cells in the mixture. This method allowed the easy quantification of specific cells subsets through bioluminescence using the combination of a streptavidin–luciferase fusion protein and a suitable biotinylated antibody.