Biotinylated fluorescent microspheres have been developed as a reagent for studying antigens and receptors expressed at the cell surface. Labeling of antigen or receptor was accomplished by crosslinking biotinylated microspheres through streptavidin to corresponding biotinylated antibodies or ligands. Detection of labeled cells by flow microfluorimetry provided an extremely sensitive means for the analysis and potential manipulation of heterogeneous cell populations. The data indicate that cells bearing fewer than 200 surface antigen-antibody complexes per cell are readily detectable by this approach. Crosslinked to a selected biotinylated peptide immunogen, biotinylated fluorescent microspheres also allowed the labeling and detection of hybridoma cells bearing antigen-specific surface immunoglobulin.
