Radioimmunoassay procedure for quantitating bacterial antibody in human sera

A RIA system was developed to detect antibodies in human sera against bacteria. Sonicates of Escherichia coli and Fusobacterium polymorphum were used as antigens to sensitize plastic-coated beads; antibodies to these antigens were detected with 125I-labeled antihuman globulin. Serum antibody titers against E. coli were determined by the serial dilution method; from the results the standard curve principle was applied in determining the relative amounts of antibodies against E. coli in serum samples tested at a single dilution. The coefficient of variation of the RIA procedure was less than 10%. Serum titers obtained by the RIA and indirect immunofluorescence test were compared; RIA was more sensitive, quantitative and objective. Absorption studies, using E. coli and F. polymorphum absorbentes against E. coli and F. polymorphum. This RIA procedure offers a combination of desirable advantages; it is sensitive, specific, objective, quantitative, and easy to perform.