A Mouse Protection Method for the Estimation of Antigenic Pneumococcal Polysaccharide in Solution

Abstract

A method is described for estimating the quantity of antigenic pneumococcal polysaccharide in solution and in blood. The method is based on the response of mice to injection of extremely small quantities of antigenic polysaccharide. Dilutions of the unknown polysaccharide solution are used to immunize mice, and the highest dilution affording complete protection against a standard challenge dose of homologous organisms is taken as the end point. A highly purified polysaccharide of known antigenic potency is used as a standard. Quantities as small as 0.01[gamma] of SI can be detected by this method. Purification of the material under test is unnecessary. The test requires about 8 days to complete in the case of SI. Although the method has been limited in application to pneumococcal materials which are antigenic in mice, it is suggested that the principle may be applicable to the evaluation of other types of antigenic substances.