Immunodiffusion using tissue sections

A simple radial immunodiffusion technique is described for determining relative antigen content of frozen tissue sections. Its use is illustrated with frozen sections of chick intestine containing the vitamin D-induced calcium-binding protein (CaBP). Diffusion of the intestinal CaBP from the sections placed on agar containing specific anti-CaBP anti-serum produced a precipitin ring, whose diameter was proportional to the CaBP content of the intestine. The technique allowed the determination of the relative antigen content in sections of tissue adjacent to others in which immunocytochemical localization or other histochemical studies were to be performed.