Cell adhesion molecules: detection with univalent second antibody.

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Abstract
Identification of cell surface molecules that play a role in cell-cell adhesion (here called cell adhesion molecules) was achieved by demonstrating the inhibitory effect of univalent antibodies that bind these molecules in an in vitro assay of cell-cell adhesion. A more convenient reagent, intact (divalent) antibody, has been avoided because it might agglutinate the cells rather than blocking cell-cell adhesion. Intact rabbit immunoglobulin directed against certain cell surface molecules of Dictyostelium discoideum blocks cell-cell adhesion when the in vitro assay is performed in the presence of univalent goat anti-rabbit antibody. Under appropriate experimental conditions, the univalent 2nd antibody blocks agglutination induced by the rabbit antibody without significantly interfering with its effect on cell-cell adhesion. This method promises to be useful for screening monoclonal antibodies raised against potential cell adhesion molecules because: it allows for the screening of large numbers of antibody samples without preparation of univalent fragments; and it requires much less antibody because of the greater affinity of divalent antibodies for antigens.