Figure.

Basic developments in antigen detection technology. In earlier systems (a and b) visualisation of the antibody-antigen complex depends on at least one additional antibody: the visualisation mechanism might be an enzyme or coloured microparticle and might be coupled to the detection antibody itself (b) or to an antibody to the detection antibody (a). With a “smart” anchor matrix (c and d), recognition of the antibody-antigen complex is based on changes to the matrix−such as change in colour or refractive index change. The capture antibody may be replaced with a specific receptor such as a toxin receptor (d)