The present invention provides peptide-ligand conjugates containing a peptide, where a free form of the peptide is capable of displacing a second ligand specific for the peptide. The invention also provides a method of selecting a cell. The method includes the steps of contacting a cell population with a peptide-ligand conjugate, wherein the conjugate comprises a first ligand specific for a cell in the population conjugated to a peptide capable of displacing a second ligand specific for the peptide, thereby forming a cell-conjugate complex; contacting the peptide-ligand conjugate with the second ligand; and isolating the cell-conjugate complex. The method can further include the step of adding a free form of the peptide to release the cell from the complex. The invention also provides a subpopulation of cells containing two or more specifically isolated cells and methods of isolating cell subpopulations. The invention additionally provides a method of diagnosing a condition using peptide-ligand conjugates. The invention further provides a kit for isolating a cell containing a peptide capable of displacing an antibody specific for the peptide and the antibody.
