Immune complexes in blood serum of calves with clinical symptoms of bronchopneumonia

Pneumonia in preruminant calves is a multifactorial disease. Infectious agents, the environment, management and the immune status of the calves are all important factors in determining the outcome of an infection. Until today, the level and composition of circulating immune complexes in preruminant calves with pneumonia have not been studied in detail. We performed this work with the aim to determine whether pneumonia in three-month-old calves is followed by changes in the immune complex level and changes in the γ-globulin level as their possible constituents. Immune complexes from the calves’ sera were isolated by polyethylene glycol (PEG) precipitation methods. Optical density at 350 nm (OD350) of redissolved precipitates was measured to determine the circulating immune complexes level. The OD350 level of PEG precipitates of calves with pneumonia at the time of diagnosis was 0.577±0.206 and it was statistically significantly higher (p<0.001) than OD350 the level of PEG precipitates of healthy calves (0.286±0.080). Electrophoretic analysis of sera and PEG precipitates showed that both slow and fast γ-globulins are found among serum and immune-complexes' γ-globulins, but the concentration of fast γ-globulins was significantly lower in sera of diseased calves. The level of PEG precipitable immune complexes was not correlated with the concentration of serum and PEG precipitable g-globulins. The results of this study have shown that by relatively simple PEG precipitation assay it is possible to detect an increased level of circulating immune complexes in calves with pneumonia. This can be used as an additional diagnostic parameter for the detection and follow up of the disease.