Antibody precipitin reaction

Sugg and Hehre43 also obtained precipitin reactions with dextran or with sterile filtrates of sucrose broth cultures of L. mesenteroides (designated for convenience strain A) and not only anti-Leuconostoc sera, but also pneumococcus Types II, XII and XX antisera. Leuconostoc organisms cultured on D-glucose broth neither stimulated the production of dextran-reactive antibodies in rabbits, nor absorbed dextran-reactive antibodies from sera, as did organisms cultured on sucrose. Absorption with the homologous bacteria (Leuconostoc, pneumococcus Types II,... 

It was noted in previous reviews (1,3) that injection of urease into rabbits elicited an antibody and that the precipitate formed between urease and its antibody still possessed catalytic activity. This indicates that the antigenic and catalytic regions are not identical. A more recent study employing horse and rat antisera (66) revealed only one major antigenic component in urease preparations and confirmed the lack of complete enzyme inhibition by the precipitin reaction. 

The binding equilibrium expressed as shown above (2.2) is actually a gross oversimplification of the situation. The heterogeneity of the binding sites and multiple valency of individual antibodies lead to formation of secondary bonds that contribute to hysteresis or ripening of the antibody-antigen complex. Its ultimate form is the polymerization of a primary complex, which happens when the antigen is also polyvalent. Formation of the polymer (precipitin reaction) renders such a reaction virtually irreversible. 

Application of 125I Radioimmunoassay to Measure Inhibition of Precipitin Reactions using Carbohydrate-Specific Antibodies, P. H. Boullanger, A. Nagpurkar, A. A. Noujaim, and R. U. Lemieux, Can. J. Biochem., 56 (1978) 1102-1108. 

Precipitin Reactions Free soluble antigen in excess of antibody Free antibody Precipitin complex deposited in vascular epithelium... 

Fig. (47). The identification of gum polysaccharides used as additives in processed foods and beverages by use of precipitin reaction with specific antibodies.

Diffusion in agar performed by the conventional method shows a strong reaction between the antibody and Man-BSA, but not with BSA (Fig. 12, plates A). However, both compounds give precipitin complex with anti-BSA serum. Oxidation of the antigens with periodate no longer gives a precipitin reaction with the anti-mannose antibodies, but has no effect on the anti-BSA antibodies. Hapten-inhibition results are also shown in Fig. 12, plates C and D. These tests are conducted with the purified antibody... 

Quantitative precipitin tests were performed as described.73 The amounts of precipitates obtained at the various concentrations were measured by the protein phenol method.74 The inhibition values are recorded in Table I. These inhibition data show that the precipitin reaction between the tetrahet-eropolysaccharide and the anti-GlcA antibodies is strongly inhibited by d-glucuronic acid, but with the exception of galacturonic acid none of the other carbohydrates were inhibitory. The data in the table also show that the carbohydrates tested did not inhibit the precipitin reaction between the polysaccharide and anti-GlcA-Rha antibodies. The monosaccharides alone cannot completely fit the active site of this antibody to give a precipitin test. 

Most, if not all, contemporary applications of immunochemical techniques are based on the reaction of antibodies with the antigen used to induce their production, to yield a very stable complex. If both antigen and antibody are present in solution, a precipitate forms as long as the antibody is in molar excess. This is known as a precipitin reaction and may be quantitated as shown in Figure 8-15. For this example a highly purified preparation of avidin was injected into a rabbit which then produced avidin-specific antibodies. Since biotin forms a very stable complex (dissociation constant with avidin, complexation of... 

Fig. 5. Quantitative precipitin reaction between crystalline hen egg albumin (Ea) and rabbit antibody (Ab) to crystalline hen egg albumin. From Heidelberger and Kendall. ...

Even when collected after overnight fasting of the animal, defatted (see below), sterilized and with a bacteriostat added, serum stored at 4° will gradually become turbid and show a deposit, principally of denatured lipoprotein. This does not lead to any loss of antibody activity although it is easily misteiken for bacterial contamination and causes anxiety for that reason. The only practical disadvantage is seen when the antiserum is used in capillary precipitin reactions, when the turbidity can obscure the result unless the antiserum is first clarified by filtration. 

Precipitation reactions are similar in principle to agglutination reactions, the difference being that the antigen is a soluble, molecular species rather than a suspended particle such as a bacterium or erythrocyte. At a certain Ab/Ag ratio, the cross-linked polymeric network of antibody and antigen loses its solubility and precipitates. This is called the precipitin reaction.11 Figure 5.6 shows how the quantity of precipitin produced varies with the quantity of antigen added, for a fixed total antibody concentration. 

Types of antigen antibody reactions that are of analytical importance are the precipitin reaction and those at a solid-liquid interface. 

Fig. 18 (68). Comparison of immunological properties of human cuprein isolated from erythrocytes (O), liver (%i), and brain(B). Quantitative precipitin reactions of rabbit antibody to erythrocuprein were performed...

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