Quantitative precipitin analyses

The quantitative precipitin analysis of antibody-antigen interactions as introduced... 

Assays for Serum Antibodies - Serum antibodies appear to be present in rather low concentrations in drug hypersensitivity in man. For example, in penicillin hypersensitivity, the serum concentrations of BPO-specific antibody protein is under 20-30 pg per ml. and most commonly under 5 pg/ml. Thus the quantitative precipitin analysis, which cannot accurately assay less than about 50 pg/ml, cannot generally be used for drug hypersensitivity. However,there are rare reports of precipitating antibody in drug allergy. 

Turbidimetry indicated that precipitate formation depended on the concentration of the protein as well as on that of the polysaccharide, the time-period of incubation, and the ratio of protein to polysaccharide.121,359,360 Precipitin curves determined turbidimetrically differed from those determined by analysis of precipitated nitrogen.360 For these reasons, early turbidimetric studies conducted on crude (rather than purified) con A are difficult to interpret. The quantitative precipitin method, wherein increasing amounts of polysaccharide or glycoprotein are added to standard aliquots of con A, and the resulting precipitate is washed, and analyzed for nitrogen, is now considered the method of choice for studying protein-polysaccharide interaction.170,320... 

An excellent review has been published by Laurell and McKay (7). These authors paid particular attendon to the different types of precipitate morphology that can be encountered with EID. They specified that the shape of precipitin loops, density of precipitates, sharpness of the precipitin line, and formation of ac acent peaks, all provide clues regarding physicochemical differences that may occur, not only between the samples and the reference solution, but also between the samples. Accurate quantitative analysis is not possible when precipitates of individual samples demonstrate abnormal appearance. If all samples produce the same type of deviation from the reference solution, then results can be given as relative rather than absolute values. 

A great variety of immunodiffusion and immunoelectrophoretic techniques have been used routinely for the qualitative and quantitative analysis of immuno-precipitins and applied to numerous research problems. Extensive reviews on this topic have been published ... 

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