![]() Cross reaction and non-identity between different antigens can be detected by this reaction.Reacting band easily visible, stable and can be stained for preservation.There are various advantages of this type of precipitation reaction – Immunodiffusion– it is generally done in 1% agar gel. Example Kahn test which is previously used diagnostic test of syphilis. Tube flocculation- Antigen and antiserum mixed in a test tube by shaking floccules will appear. Example VDRL slide test for detection of antibodies against syphilis – Slide flocculation – The drop of antigen and antiserum on a slide and mixed it by shaking then floccules will appear. Flocculation test – This test can be done in the slide and in the tube.Ring test – in this test we layered the antigen solution over the column of antibody in a narrow tube and then we see the precipitate at the junction of two liquids.Example – C-reactive protein (CRP) and Lancefield grouping of streptococci.Various types of precipitation reaction:- 1.) Precipitation reaction in liquid In the case of excess antigens, no cross-linkages occur now antibodies are insufficient to the formation of lattice formation. ![]() In the case of excess antibodies, so no cross-linkage will form, many antibodies are there but due to insufficient amount of antigen no lattice formation takes place. Precipitation can occur in the zone of equivalence where the amount of antigen and antibody must be equal and lattice formation takes place by which insoluble precipitate can be seen. The mechanism of precipitation reaction lies under the lattice hypothesis proposed by Marrack in 1934.Īccording to this hypothesis when the multivalent antigen reacts with bivalent antibodies then precipitation occurs due to the formation of the large lattice. Radioimmunoassay (RIA) – Principle, Procedure, Advantages, Disadvantages, & Applications
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