Patent ID: 7776562

Claim:
A method for the reversible staining of a target cell, said target cell comprising a receptor molecule on the surface thereof, with a detectable label, the method comprising: contacting a population of cells comprising said target cell with (i) a population of monovalent conjugates, each monovalent conjugate comprising a single ligand which specifically binds to said receptor molecule, and each monovalent conjugate comprising at least one first partner conjugated to said single ligand, wherein the dissociation constant (k d ) for the binding between said ligand of said monovalent conjugate and said receptor molecule is in the range of 10 −2 to 10 −7 M; (ii) a population of binding reagents, each binding reagent comprising at least two binding sites for said first partner wherein the populations of (i) and (ii) form a population of multivalent binding reagents that bind to said target cell; and (iii) said detectable label bound to said multivalent binding reagents, wherein (a) said first partner comprises biotin and said binding reagent comprises a streptavidin analog or an avidin analog that reversibly binds to biotin, (b) said first partner comprises a biotin analog that reversibly binds to streptavidin or avidin and said binding reagent comprises streptavidin, avidin, a streptavidin analog, or an avidin analog that reversibly binds to said biotin analog, or (c) said first partner comprises a streptavidin or avidin binding peptide and said binding reagent comprises streptavidin, avidin, a streptavidin analog, or an avidin analog that reversibly binds to said streptavidin or avidin binding peptide, and wherein said target cell is stained by binding of said multivalent binding reagent to said target cell, and wherein staining of said target cell is reversible upon disruption of the binding between said first partners and said binding sites of said binding reagent.