Estimation of the Immune Response to Bacterial Antigen by Means of Hemagglutinating Autoanalyzer

No convenient procedures are currently available for the estimation of antibody to bacterial antigen on a continuous scale, and antibacterial titers are usually reported as the reciprocal of the highest dilution of the sample resulting in agglu-tination. We report here the adaptation of a hemagglutinating auto analyzer for the determination of the level of antibody in rats immunized with killed Esche-ri~hia coli antigen. Antibody titers are reported on a scale that is continuous and not restricted to the limitations of serial dilution end points. The method is repro-ducible and specific and is much more sensitive than manual methods. The technique of agglutination of a suspension of killed bacteria by serial dilutions of serum for the estimation of serum antibody activity has been in use since the earliest days of microbiology. Although a number of advances have been made in the sensitivity with which levels of antibody in serum can be determined, traditional and con