[Significance and course of a cold agglutinin in Eperythrozoon suis infection of swine].

After infection with Eperythrozoon suis, pigs began to produce cold agglutinins of immunoglobulin type IgM, that because of the similarity between the pathogenic antigen and antigen on the erythrocyte membrane caused agglomeration. The progression of this cold agglutinin was measured with an enzyme immunoassay especially invented for this purpose, and compared with serum-IgM, agglutination strength, pathogenic effect as well as number of erythrocytes in the blood. The cold agglutinin extracted from the erythrocyte membrane at 40 degrees C showed, in comparison to the initial figures, a higher level (1259 micrograms/ml) at 6 days after the illness peak, reaching its maximum (2435 micrograms/ml) at 12 days. Similar results were achieved at lower extraction temperatures (22 degrees C, 0 degree C). A high correlation could be shown between the levels of IgM and of cold agglutinin, as well as the parallel increase in the agglutination strength of the blood. At the time of maximal pathogenic effect, no agglutination of blood was observed. The number of erythrocytes decreased in acute phases of an attack to a constant mean of 2.32 Mill./microliters of blood and then increased, at the same rate as the cold agglutinin level decreased, almost reaching normal values. These experiments confirm the fact that an organism following an infection with Eperythrozoon suis, begins to produce cold agglutinins. Due to structural similarities between the pathogen and the erythrocyte antigen the cold agglutinin causes temperature dependent agglutination.(ABSTRACT TRUNCATED AT 250 WORDS)