Protein conjugated microspheres are offered as: antibodies, Protein A, and Protein G covalently coupled to fluorescent YG, non-fluorescent, and blue dyed polystyrene microspheres. Antibody conjugated microspheres can be used to detect trace amounts of specific antigens in solution and to deplete them from solution. Microspheres coupled with Protein A and Protein G will bind to the Fc portion of antibodies raised in most mammals.