Surface located antigens

Ig) family of proteins. B7 is located on the surface of antigen-presenting cells (ARCS) and docks on the CD28 receptor of T cells. 

In that case a cocktail of antibodies directed to antigens located at surfaces of different cells is necessary (Poste and Kirsh,... 

An IgG-antibody against an individual ribosomal protein binds specifically only to this protein in a ribosomal subunit. Since the antibody is divalent it can form a bridge between the identical proteins in two subunits, leading to a dimer that can be examined under Ae electron microscope. The location of the bound antibody on the subunit surface can be determined, defining the position of the antigenic determinant of a particular protein. The method relies on the fact that IgG-antibodies are able to react with specific proteins within the intact ribosomal subunits and that both subunits have discernible shapes with recognizable morphological landmarks. 

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