![]() Interaction between gel matrix and reactants.Immunodiffusion takes place through the intervening agar media whose rate is influenced or affected by the following factors like: In this type, the precipitation method is performed in the ordinary media like nutrient agar media. The example of tube flocculation tests is RPR (Rapid Plasma Reagin) and VDRL (Venereal Disease Research Laboratory) test. ![]() Tube flocculation test: In this, the procedure is the same as slide flocculation test, but the only difference is that it is performed in a test tube instead of slide.If clumping between antigen and antibody occurs, the slide test will give a positive result and vice versa. Then over the antiserum, a drop of test antigen is added, followed by thorough mixing. Slide flocculation test: In slide test first, the drop of antiserum is added onto the clean glass slide.This test can be performed in either of the two ways: Then, over incubation of the reactants, the precipitation reaction occurs between antigen and antibody and a white precipitate forms at the junction. After that, test antigen is added to the solution. In the ring test, the antibodies which are present in the serum is first taken in the test tube. It consists of two methods, namely a ring and flocculation test. In this type, the precipitation method is performed in the liquid media or solution. The least soluble antigens and antibodies form a complex at the point of equivalence, whereas the free antigens and antibodies remain as the supernatant.īased on the type of matrix, the methods of precipitation reaction include: In the equivalence zone, cross-linkage occurs between the reactants that result in the formation of the antigen-antibody complex as a visible ring or line of a precipitate. At the equivalence region, the ratio of both antigen and antibody is equal, which brings out the formation of lattice or cross-linked structure. Lattice: It appears as a cross-linked structure formed by the cross-linking of Ag and Ab to form an immunocomplex.Ī precipitation reaction is based on the principle of “ antigen-antibody reaction”, which occurs at the equivalence zone.Precipitinogen: The soluble antigens act like precipitinogens, which induce the formation of precipitin, i.e.Precipitin: The soluble antibodies behave like precipitins, which react with the soluble antigens and bring a precipitate formation in the form of a visible insoluble mass.There are specific terms, which we should know before proceeding to the theory of precipitation reaction. Precipitin is an antibody which reacts with a respective antigen to form a “ Precipitate”. The lattice formed by antigen and antibody is visible, either in the form of precipitin ring or in the way of precipitin line. The antigen and antibody react with each other to form an immunocomplex or lattice at the zone of equivalence (Abs and Ags are at equilibrium). both antigen and antibody diffuse either in one dimension or two dimensions in liquid or semi-solid media. Precipitation in Agar by ImmunodiffusionĪ precipitation reaction is an immuno or serological assay where the two reactants, i.e.Here, we will focus on the definition, principle and methods of the precipitation reaction in solution and agar (by diffusion and electrophoresis) along with the meaning of some important terms relative to this context. Thus, the end product appears as a precipitate, which can be measured by devices like turbidometer and nephelometer. For the reaction to occur, the concentration of both antigen and antibody must be equal, which in turn produce a visible mass of precipitate or lattice. If anyone’s concentration (either antigen or antibody) exceeds, the immunocomplex will not form.
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