In most cases the antigen and the immunogen two words can be used interchangeably, the difference is very small. They are respectively refers to a molecule with two types of interaction between the immune system. A immunogen refers to can make a biological tissues of the immune system to produce an immune response, and a antigen is combined with the child of this kind of immune response, so must have antigen immunogen, but is not necessarily immunogen antigen, we here especially to the product of the immune response - general antigen antibody molecules.Identify areas (epitopes) refers to an antigen molecules in a combined with antibodies to direct a particular sequence, for any antigen protein, are likely to have multiple antibodies recognition area, for the production of antibodies, easily antibodies to identify parts recognition area is most ideal.