Stimulation and suppression of the oxygenation activity of porcine pulmonary alveolar macrophages by Actinobacillus pleuropneumoniae and its metabolites

P. Dom From the Laboratory of Veterinary Bacteriology, Faculty of Veterinary Medicine, University of Gent, Casinoplein 24, B-9000 Gent, Belgium (Dom, Haese-brouck), and the Institute for Molecular Biology, University of Brussels, Paardenstraat 65, B-1640 Sint Genesius Rode, Belgium (De Baetselier).

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F. Haesebrouck From the Laboratory of Veterinary Bacteriology, Faculty of Veterinary Medicine, University of Gent, Casinoplein 24, B-9000 Gent, Belgium (Dom, Haese-brouck), and the Institute for Molecular Biology, University of Brussels, Paardenstraat 65, B-1640 Sint Genesius Rode, Belgium (De Baetselier).

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P. De Baetselier From the Laboratory of Veterinary Bacteriology, Faculty of Veterinary Medicine, University of Gent, Casinoplein 24, B-9000 Gent, Belgium (Dom, Haese-brouck), and the Institute for Molecular Biology, University of Brussels, Paardenstraat 65, B-1640 Sint Genesius Rode, Belgium (De Baetselier).

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Summary

The effects of Actinobacillus (Haemophilus) pleuro-pneumoniae and its metabolites on the oxygenation activity of porcine pulmonary alveolar macrophages (pam) were studied, using a chemiluminescence technique. Actinobacillus pleuropneumoniae strains of serotypes 2, 3, and 9 in a dose of 1, 10, and 100 colony-forming units/ macrophage first stimulated the oxygen radical production of pam. After having reached a peak value, oxygenation activity decreased, finally resulting in total suppression of pam. All these effects were neutralized by homologous convalescent pig sera that had been adsorbed onto inactivated A pleuropneumoniae strains. Moreover, cross-neutralization was shown between serotypes 2 and 3. Inactivated A pleuropneumoniae strains did not influence the oxidative activity of pam. Undiluted and lower dilutions of sterile A pleuropneumoniae culture supernatants were toxic for pam, whereas higher dilutions of the supernatants stimulated oxygen radical production of the macrophages. These effects were heat-sensitive and were neutralized by homologous convalescent pig sera. Cross-neutralization was shown between serotypes 2 and 3. These findings indicated that stimulation and inhibition of the oxygenation activity of pam are attributable to heat-sensitive metabolites produced by A pleuropneumoniae.

Summary

The effects of Actinobacillus (Haemophilus) pleuro-pneumoniae and its metabolites on the oxygenation activity of porcine pulmonary alveolar macrophages (pam) were studied, using a chemiluminescence technique. Actinobacillus pleuropneumoniae strains of serotypes 2, 3, and 9 in a dose of 1, 10, and 100 colony-forming units/ macrophage first stimulated the oxygen radical production of pam. After having reached a peak value, oxygenation activity decreased, finally resulting in total suppression of pam. All these effects were neutralized by homologous convalescent pig sera that had been adsorbed onto inactivated A pleuropneumoniae strains. Moreover, cross-neutralization was shown between serotypes 2 and 3. Inactivated A pleuropneumoniae strains did not influence the oxidative activity of pam. Undiluted and lower dilutions of sterile A pleuropneumoniae culture supernatants were toxic for pam, whereas higher dilutions of the supernatants stimulated oxygen radical production of the macrophages. These effects were heat-sensitive and were neutralized by homologous convalescent pig sera. Cross-neutralization was shown between serotypes 2 and 3. These findings indicated that stimulation and inhibition of the oxygenation activity of pam are attributable to heat-sensitive metabolites produced by A pleuropneumoniae.

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