Fractionation of mast cell components for studies of ligand-receptor binding at the plasma membrane

This communication describes a simple procedure for fractionating mast cells producing plasma membranes and intact granules. Mast cells were purified over a bovine serum albumin density gradient and disrupted under conditions in which no histamine was released. Iodinated immunoglobulin E (IgE) bound to the cells served as a marker for the plasma membrane fraction. Employing a discontinuous sucrose gradient the plasma membrane and granule fractions were separated. The specific activity of the IgE binding to the isolated plasma membrane fractions was 10-fold higher compared with that of the IgE binding to intact cells.