LOCALIZATION AND QUANTIFICATION OF EPIDERMAL GROWTH-FACTOR RECEPTORS ON SINGLE CELLS BY CONFOCAL LASER SCANNING MICROSCOPY

We have established a method for quantifying binding of fluorescence-labeled growth factors to their receptors on single cells in situ with the confocal laser scanning microscope (CLSM). Biotinylated epidermal growth factor (EGF) coupled to phycoerythrin-labeled anti-biotin was used to compare the levels of fluorescence on three different cell types for which the number of EGF factors was known from Scatchard analysis of [I-125]-EGF binding. The results showed that as few as 10,000 receptors/cell were detectable above background. This method will provide a rapid and quantifiable alternative to autoradiography for ligand binding to single cells in situ.