Immunodiffusion in Agarose Gels
The antigen-antibody complex forms an insoluble precipitate when the reaction is carried out both in solution and gels. Performing such reactions in agarose gel is advantageous because of higher sensitivity and resolution.
Immunodiffusion in gels is often classified as single or double diffusion. In single diffusion technique, the antigen (Ag) is usually allowed to diffuse into a gel containing the gel antiserum/antibody (Ab). On the other hand, in the double diffusion technique, both the antigen and antibody are allowed to diffuse into the gel and meet each other. A lot of qualitative and quantitative information on the antigen can be derived from the diffusion techniques. This is the simple technique to test for the antibody titre during immunization and to study the antigen-antibody reactions in gels.
The antigen and antibody react to produce the antigen-antibody complex. At equilibrium, the complex produced is immobile and forms a thin band of (protein) precipitin. The precipitin is visualized either directly or after protein staining for interpretation.