The MagDot is a dual-purpose reagent, it combines quantum dots and superparamagnetic iron oxide particles within the same nanoparticle. Cells labeled with MagDots targeting specific antigens will be both fluorescent and magnetic. Therefore, after labeling cells of interest, one can look at the feed to determine the percent positive fluorescently via flow cytometry, and then place the labeled cells in a magnetic separator and analyze both the magnetic (for the enrichment) and the nonmagnetic (for the depletion) of targeted cells without the need for further fluorescent labeling. The RPAT4 antibody conjugated to this MagDot recognizes human CD4, a 55 kDa cell surface glycoprotein that is primarily expressed on a subpopulation of T lymphocytes, on peripheral blood monocytes and on tissue macrophages.