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A macrophage-suppressing 40-kD protein in a case of pulmonary alveolar proteinosis
J Müller-Quernheim1, R E Schopf, P Benes
1Abteilung für Pneumologie, Johannes-Gutenberg-Universität Mainz.
Abstract:
Pulmonary alveolar proteinosis (PAP) is a rare disease of unknown etiology. Macrophage dysfunctions are claimed to be involved in the pathogenesis. We investigated phagocytosis and oxidative metabolism of alveolar macrophages in a case of pulmonary alveolar proteinosis. These cells phagocytize normally and phagocytizable stimulants cause a normal oxidative burst. In response to the membrane signals phorbolmyristate acetate and aggregated immunoglobulin, however, no stimulated turnover of the oxidative metabolism can be observed. A 40-kD protein found in the lavage fluid mediates this macrophage-inhibiting effect. This phenomenon may contribute to the frequent opportunistic infections seen in PAP patients. It can be concluded from our data that the high frequency of infections with opportunistic species in these patients can be reduced by therapeutic bronchoalveolar lavage. By this procedure the abnormal macrophage-suppressing protein can be washed out of the lung at an early stage of the disease.
Insights
Pulmonary alveolar proteinosis (PAP) involves macrophage dysfunction. A specific protein inhibits macrophage oxidative metabolism, potentially causing infections, but bronchoalveolar lavage may help.
Area of Science:
- Immunology
- Pulmonology
- Cell Biology
Background:
- Pulmonary alveolar proteinosis (PAP) is a rare lung disease with unknown causes, often linked to macrophage dysfunction.
- Investigating alveolar macrophage function is crucial for understanding PAP pathogenesis and associated infections.
Observation:
- Alveolar macrophages in PAP patients exhibit normal phagocytosis and oxidative burst in response to certain stimulants.
- However, these macrophages show no stimulated oxidative metabolism when exposed to phorbolmyristate acetate or aggregated immunoglobulin.
Findings:
- A 40-kD protein isolated from lavage fluid was identified as the mediator of this macrophage-inhibiting effect.
- This inhibition of macrophage oxidative metabolism is a key finding in the studied case of PAP.
Implications:
- The observed macrophage dysfunction may explain the high incidence of opportunistic infections in PAP patients.
- Therapeutic bronchoalveolar lavage could be a viable early-stage treatment to remove the inhibitory protein and reduce infection risk.