The dot blot (immunoblot) technique is used to determine the presence of an antigen. Clinical diagnostic kits employ the principles of the dot blot. In this experiment, antigens are absorbed to a membrane that is then treated with an antigen-specific antibody solution and then a secondary antibody conjugated to an enzyme. The enzyme-substrate reaction generates a color product that precipitates onto the membrane, indicating a positive reaction. No human serum is used in this experiment.