Isolation of cold agglutinins in Eperythrozoon suis-infected pigs

A simple and reliable procedure is described for isolating the cold agglutinins associated with Eperythrozoon suis-infection in swine. After initiating microagglutination by cooling the blood samples, the erythrocytes were separated by density-gradient centrifugation using Ficoll-Paque, resuspended in RPMI-medium and warmed to 40 degrees C. The cold agglutinins could be removed from the supernatant by a subsequent centrifugation. Double immunodiffusion, polyacrylamide gel electrophoresis and immunoblotting showed that the cold agglutinins isolated consisted of IgM antibodies exclusively. Their ability to induce agglutination in cooled erythrocytes from healthy pigs confirmed that they were genuine cold agglutinins. The method paves the way for more detailed investigation into the mechanisms of this agglutinating disease.