Basic Immunology Precipitation Presented by : 1 – Othman naif almutairi 2 – khader saleh alghamdi 3 – turki khaled almutairi DR : Mohammad khatatnah

:Introduction A. General characteristics of antigen/antibody reactions. 1. Sensitization is the basic reaction of an antigen and antibody binding. 2. Can measure either antigen or antibody in a. patient sample

3. Factors that affect antigen/antibody reactions include : A. Concentration of the reactants B. Temperature C. Length of incubation D. pH of the test system. 4. Antigen/Antibody reactions

Precipitation # Precipitation reactions are also dependent on the amount of antigen and antibody present in the test system 1 - Prozone occurs when excess antibody is present. a. So much antibody is present that all antigen sites are coated and lattice formation cannot occur. b. Results in false negative reaction.

2 - Postzone phenomenon occurs when excess antigen is present. a. There is so much antigen present that the antibody molecules bind in such a way that lattice formation cannot occur. b. The antibody may bind to antigen sites on two separate molecules, sensitization may occur, but the binding is not on enough adjacent molecules to form lattice. c. Results in a false negative reaction.

3 - Zone of equivalence is when antigen and antibody are present in optimal proportions, sufficient antibodies can bind to antigens on adjacent molecules resulting in lattice formation.

Principle of reaction

formation Precipitation

precipitation experiment immunology

Capillary tube precipitation (Ring Test) Qualitative test Layer Ag over Ab Simplest test Qualitative Precipitate occurs at the interface of the two reagents, forming a ring.

Ring test

Radial Immunodiffusion (RID) Quantitative test The technique of quantitative radial immunodiffusion is based upon the reaction between an Ag, and a specific Ab during a diffusion period. The Ag-Ab interaction is manifested by a well-defined ring of precipitation around the Ag well.

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