VLD 421: Veterinary Clinical Biochemistry and Laboratory Diagnosis-II (0+1)

INTRODUCTION

• Immunodiffusion (ID) is a classic technique for detecting antibody-antigen interactions based on the theory of double diffusion originally described by Oudin and Ouchterlony.
• An important property of many antibodies is their ability to precipitate antigens in the solution.
• Antigens and antibodies are placed into separate wells that are cut into a gel matrix and allowed to diffuse towards each other.
• If the reaction is positive, a precipitate forms that appears as an opaque line.
• The precipitation reaction occurs when the antigen and antibody concentrations are combined at near equivalent proportions.
• Agarose is a purified substance derived from agar.
• Gels from 1-2% agar or agarose solution are semi-solid media that provide the pore size sufficiently large for the free diffusion of immunoreactants until antigen and antibody reach the optimal concentration for lattice formation.

Advantages

• Gelling agent contains precipitin brighteners for easy visualization.
• Immunodiffusion plates contain diffusion enhancers to help speed the interaction process.
• Excellent precipitin bands with antibodies from all species (including rabbit antibodies).
• Gels can be washed, dried and stained for a permanent record.