Quantitative measurement of precipitating antibodies and standardization of Streptococcus group B antisera by the reverse radial immunodiffusion technique

A comparative study was made of the reverse radial immunodiffusion (RRID) technique and the quantitative precipitin test for determining the amount of precipitable antibodies present in streptococcus group B antisera. The coefficient of correlation between the 2 tests was 0.963 when a purified carbohydrate antigen was used. The results of this study show that: (1) a group B antiserum should contain at least 3 mg of precipitable antibodies per ml to ensure that it will react with acid extracts of group B diagnostic cultures; and (2) the RRID technique is an accurate and simple procedure for determining the amount of precipitable antibody present in an antiserum, and it could be used for the standardization of these diagnostic reagents. A method for preparing the group B carbohydrate antigen used in the RRID and quantitative precipitin tests is described.

Quantitative measurement of precipitating antibodies in streptococcal grouping antisera by the single radial immunodiffusion technique

A comparative study was made of the single radial immunodiffusion test and the classical quantitative precipitin test for determining the amount of precipitable antibodies present in streptococcal groups A and C antisera. The potency of 21 group A and 54 group C antisera was determined by both methods; purified group-specific carbohydrates were used as antigens. The coefficient of correlation between the results from the two methods was 0.976 for group A antisera and 0.946 for group C antisera. When the concentration of antigen, the volume of antiserum used, and the depth of the antigen-agar mixture are kept constant, the diameter of the precipitin disc is directly related to the concentration of precipitable antibodies present in the antiserum. The use of the radial immunodiffusion test for evaluating and standardizing streptococcal grouping antisera is discussed as well as the advantages and disadvantages of using a concentrated vaccine for producing these antisera.