Surfactant apoprotein in nonmalignant pulmonary disorders

Area of Science:

• Pulmonary Pathology
• Cell Biology
• Immunohistochemistry

Background:

• Pulmonary alveolar proteinosis is characterized by intra-alveolar accumulation of proteinaceous material.
• The exact mechanisms leading to this accumulation, particularly the role of pulmonary surfactant, are not fully understood.

Purpose of the Study:

• To investigate the presence and distribution of surfactant apoprotein and other proteins in nonmalignant lung disorders.
• To elucidate the cellular source and composition of intra-alveolar material in pulmonary alveolar proteinosis.

Main Methods:

• Immunoperoxidase staining of formalin-fixed, paraffin-embedded lung tissue.
• Antibodies used included those specific for surfactant apoprotein, IgG, IgM, IgA, albumin, fibrinogen, and lysozyme.

Main Results:

• Normal Type II pneumocytes showed surfactant apoprotein staining in the perinuclear region.
• Reactive Type II pneumocytes exhibited increased apoprotein staining, suggesting a response to lung injury.
• Intra-alveolar material in pulmonary alveolar proteinosis stained intensely for surfactant apoprotein, confirming surfactant presence.
• Type II pneumocytes in affected lungs showed hyperplasia and hypertrophy.
• Macrophages stained positively for lysozyme.

Conclusions:

• The proteinaceous material in pulmonary alveolar proteinosis contains pulmonary surfactant.
• The condition may result from both overproduction and deficient removal of pulmonary surfactant.
• Increased surfactant apoprotein staining in reactive pneumocytes indicates a nonspecific response to lung injury.