Measurement of Antigen - Antibody Complexes in Salmonella gallinarum Infection.

Following oral infection of a 12-week-old chicken with an overnight broth culture of Salm. gallinarum, serum was removed on the 9th day and tested for the presence of haemagglutinating antibody using erythrocytes modified with a Westphal lipopolysaccharide extract of Salm. gallinarum. The serum was found to have a high titre and on ’Sephadex’ fractionation and ultracentrifugal preparation showed a marked IgM response. Spectrophotometric measurements were made of interactions between the O-antigen extract and the whole serum or its component IgM and IgG fractions. Hapten-antibody complexes were measurable with the whole serum and the IgM fraction, but no complexes were detected with the IgG fraction under the conditions of the experiment.