Abstract: The invention is directed to a method for enriching target cells from a sample of cells characterized by: a) contacting the sample with a cell aggregation agent and first magnetic particles having an iron content of 0.1 pg to 5000 pg, coupled to a first antigen recognizing moiety; and second magnetic particles having an iron content of 0.05 fg to 100 fg and coupled to a second antigen recognizing moiety to obtain mixture a) b) applying a first magnetic field gradient to the mixture a) thereby removing the cells bound to the first antigen recognizing moiety coupled to the first magnetic particles, to obtain a mixture b) and obtaining an agglomerate comprising the cells of mixture a) bound to the cell aggregation agent c) applying a second magnetic field gradient to the mixture b) thereby immobilizing the cells bound to the second antigen recognizing moiety d) recovering the immobilized cells from the second magnetic field gradient as target cells.

Abstract: 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. The ligand moiety of the biotinylated ligand may be separated by a spacer group consisting of polyethylene glycol. 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.