Abstract: The invention provides multimeric receptor-binding complexes, including chemokine tetramers, useful for recognizing and binding receptors bound to the surface of a wide variety of cells. The binding complexes are useful for identifying and isolating cells according to their specific receptors, screening for cells having a specific receptor or constellation of receptors, and introducing exogenous molecules (e.g., nucleic acids and toxins) into cells. Methods of producing the complexes and other uses are also described.