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

PRINCIPLE

• Agar gel precipitation test is qualitative assessment of presence of anitigen in sample or antibody in serum . 
• Precipitation reactions are generally prepared as agar diffusion reactions, to make precipitates more visible. An agarose gel is used as a matrix for combining diffusion with precipitation. The reactants diffuse through the gel towards each other and precipitation results when the equivalence points have been reached.
• The precipitation reaction is a soluble antigen reacted with its homologus antibody in the presence of electrolytes at the optimum proportion to produce an insoluble antigen – antibody complex precipitate. The precipitation reaction is highly specific and very sensitive for the detection of antigen . It is important to bear in mind that antigens used in precipitation reactions are of molecular size and not cellular.
• A single antigen will give rise to a single line of precipitation in the presence of its homologous antibody. When two antigens are present in a system, each behaves independently of the other. Therefore, if several bands of precipitation are detected, there are at least as many antigen-antibody combinations present.