sandwich technique

sandwich technique, a method of identifying antibodies or antibody-synthesizing cells in a tissue preparation. A solution containing a specific antigen is applied to the preparation. If antibodies to the antigen are present in the tissue, they will bind to the antigen. Unbound antigen is washed away, and then a fluorochrome-labeled antibody specific for the antigen is added. The result is a complex of antigen sandwiched between antibodies, which can be detected by fluorescence microscopy. See also ELISA.