Prospective on cell surface labeling using the hapten-sandwich method: an integrated approach.

Specific molecular units on the surface membranes of cells were tagged with markers visible in fluorescence, transmission and scanning electron microscopy. The Hapten-sandwich method does this by the sequential application of hapten-modified anti-cell-surface antibody, anti-hapten antibody and a hapten-modified marker. Details are given for the preparation and testing of the various reagents used in this method. The specificity and efficiency of Hapten-sandwich coupling of hemocyanin to mammary tumor virus (MTV) budding from breast tumor cells was demonstrated by quantitative transmission electron microscopy. Con A and anti-saccharide antibodies were used to demonstrate the presence of various sugars on the surfaces of the mammary tumor cells using fluorescence, transmission and scannings electron microscopy. Some samples were doubly labeled for the simultaneous presence of two different sugars. Light and electron microscopy were used to show that several hormones (insulin(I), hydrocortisone(F), and prolactin) greatly affect the expression of tumor virus and the kind and density of cell surface sugars on mammary tumor cells. Individual cells produced virus and expressed surface sugars independently. A micro-scanning densitometer was used to quantitate the results from fluorescence microscopy. Future advances in cell labeling including other applications of the Hapten-sandwich method, and problems such as the quantitation of electron microscopy labeling are discussed.