The invention is directed to a releasable conjugate comprising a biotinylated ligand having a biotin moiety, a ligand moiety (Ligand1) and a biotin-binding molecule (bbm) bound to the biotin moiety of the biotinylated ligand characterized in that the biotin moiety and the ligand moiety of the biotinylated ligand are separated by a spacer group consisting of polyethylene glycol according to the general formula Iwith n = 1 - 500, and X, Y = same or different, substituted alkyl groups having 1 to 20 carbon atoms with amine, amide, and/or thioether residues, wherein the ligand is a first antibody and the biotin-binding molecule (bbm) is a second antibody which comprises a detection means selected from the group chromophor unit, fluorescence unit, radioactive unit, and solid support.Furthermore, the invention relates to a method for cleaving the releasable conjugate by providing biotin or streptavidin and an auxiliary release agent in a sufficient concentration to displace the biotin-binding molecule (bbm) from the biotin moiety of the biotinylated ligand and a method for separation of target cells from a cell sample utilizing the conjugate.
