Precipitin tests

Five out of six patients gave a positive precipitin test. Malarial antigen was extracted from human brain for gel diffusion tests. 

Various factors that influence the results of precipitin tests have been discussed by Matthews.14 In particular, the size of the reacting antigen... 

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. 

Quantitative hapten inhibition tests were also performed.73 The amount of myeloma protein-dextran complex that formed in individual tests was measured by the determination of protein in the precipitate, using a colorimetric method.74 The precipitin tests were performed in a final volume of 0.2 mL, which comprised 80 pL of 0.02 M phosphate buffer of pH 7, 20 pL of ascitic fluid or purified myeloma protein, and 100 pL of dextran B-1355S solution in phosphate buffer of pH 7. The extent to which glucose... 

Precipitin tests As the name implies, precipitin tests rely on the fact that when the appropriate ratio of antibody and antigen are mixed together, immune complexes of antibodies and soluble antigens come out of solution, settling to form a visible precipitate. The antibody-antigen precipitate formation can be plotted as a curve, and interaction is maximal at the top of the curve (termed the zone of equivalence) shown in Figure 10.2. This technique can be used to quantify the antibody content of a solution. 

Antisera to be used in capillary precipitin tests must be crystal clear so that the faint ring of precipitation can be easily seen. Untreated sera become turbid on storage, due to precipitation of denatured lipoprotein such precipitates can be removed by membrane filtration prior to use, but it is usually better to reduce the severity of the problem by extracting the bulk of the lipoprotein at the time the serum is first prepared. 

Optimal precipitation requires application of the well known principles of quantitative precipitin tests. In general these involve use of an ionic strength approximating 0.15, pH between 6.5 and 8.5, temperature between 0° and 37°, and sufficient time to ensure that the reaction reaches equilibrium. In addition, the second antibody must be present in sufficient but not excessive amounts in order to ensure maximal precipitation of the nonimmune y-globulin (and thereby the primary antibody). 

A further quantity of the same substance was prepared by these workers and purified by repeated precipitation with lead acetate and ammonia. The product had [q ]d + 67.7° which changed to —10° after hydrolysis with dilute sulfuric acid for four hours. The amount of reducing sugar present was 75.6%. Mannose, D-arabinose and an unidentified sugar acid were obtained from the hydrolyzate. The substance did not produce a skin reaction, nor did it stimulate antibody formation. It reacted with immune serum in high dilution (1 2,000,000) in the precipitin test. It was claimed that this product was closely related to the polysaccharide isolated by Laidlaw and Dudley. ... 

The quality control of immunoglobulins includes potency tests and conventional tests for safety and sterility. The potency tests consist of toxin or virus neutralization tests that parallel those used for the potency assay of immune sera, except that for in-process control of some immunoglobulins wider use is made of in vitro assays. In addition to the safety and sterility tests, total protein is determined by nitrogen estimations, the protein composition by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and molecular size by high performance liquid chromatography. The presence of immunoglobulins derived from species other than humans is excluded by precipitin tests. Table 23.4... 

C19. Crowle, A. J., Enhancement by various cations of the double-diffusion precipitin test. Intern. Arch. Allergy Appl. Immunol. 16, 113-125 (1960). 

Jll. Jonckheer, M. H., The electro-precipitin test as a quantitative method. Protides Biol. Fluids, Proc. Colloq. 11, 393-397 (1964). 

Wll. Watson, D., and Whinfrey, H., An electro-precipitin test for thyroglobulin antibodies. Lancet il, 1375 (1958). 

W4. Wilson, M. W., and Pringle, B. H., Experimental studies of the agar-plate precipitin test of Ouchterlony. J. Immunol. 73, 232 (1954). 

Bryan GC, Scudder J (1952) Dextran and pneumococcus polysaccharide cross-reactivity in skin tests and serum precipitin tests. Ann NY Acad Sci 55 477-478 Bygdeman S, Eliasson R (1967) Effect of dextrans on platelet adhesiveness and aggregation. Scand J Clin Lab Invest 20 17-23... 

Twenty-seven simple substances containing the phenylarsonic acid group as haptenic group were prepared and used in precipitin tests with antisera made by injecting rabbits with azo-phenylarsonic acid sheep serum. 

Immunodiffusion test A serologic test similar to the precipitin test but carried out in agar gel medium. 

Precipitin test Immunological test used to detect antibodies that is based on the precipitation reaction. 

The observation that the serum inhibition of Candida albicans seen in normal patients (38) is lost in patients with Candida septicemia (12) raises interesting possibilities. In contradistinction to this we have found that patients can develop positive precipitin tests from Candida (47) without clinical evidence of can-didemia (blood culture negative, no fever)(16). These patients are receiving the "amphotericin flush" (15) (see below), and this implies that catheter-related candidemia may be dependent on repetitive inoculation to produce clinical candidemia. Finally, there is... 

These relatively recent data, obtained by using IgG fractions of antisera in precipitin tests, are selected for presentation since whole antiserum was used in most earlier investigations the use of serum complicates the quantitative interpretation of results because albumin binds many anions. 

Data described so far were based on qualitative precipitin tests in agar gel. Quantitative studies were carried out to assess the capacity of isolated H and L chains to react with rabbit anti-D antibodies directed to a human IgG myeloma protein having L chains of the k type (76). Substantial inhibitory activity was observed in an autologous recombinant, comprising H and L chains of the immunogen, but not in isolated L chains or in recombinants in which only one of the chains was derived from the immunogen. Very similar results were obtained with rabbit anti-D antibodies to two other monotypic proteins of the k type, one IgG and one IgM (99). 

Quite different results have been obtained when cross-reactions were investigated by inhibition of specific precipitation. In several systems nonspecific IgG inhibited, partially or completely, the precipitation in liquid medium of human IgG myeloma proteins by rabbit anti-D antisera classical precipitin tests were utilized (18,97). 

Ferritin or apoferritin, several times recrystallizeu, injected into rabbits subcutaneously, behaves as an antigen and readily produces a specific antibody in the form of a precipitin (7). Ferritin and apoferritin are indistinguishable immunologically. The precipitin is specific for the animal species but not for the particular organ from which it is prepared. This precipitin test is very sensitive and reveals the presence of ferritin in such org< ns as are too low in ferritin content to allow ready... 

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