Alveolar macrophage membrane phospholipid methylation in sarcoidosis and hypersensitivity pneumonitis.

Methylation of phospholipids seems to be an essential step in the recognition and transduction of regulatory signals by eukaryotic cells. Phosphatidylethanolamine methylation was compared in alveolar macrophage membrane from patients presenting with pulmonary sarcoidosis or hypersensitivity pneumonitis and control subjects. Phosphatidylethanolamine methyltransferase (PMT1) activity was determined by various measures of incorporation of tritiated methyl group from (3H) S-adenosyl-L-methionine in membrane phospholipids. Tritiated methyl group incorporation in macrophage membrane was higher in some patients presenting with sarcoidosis or hypersensitivity pneumonitis, than in controls. PMT1 activity was found to be higher in sarcoidosis patients with a positive gallium lung scan. As lipids play an important role during macrophage activation and cell interaction, although a wide heterogeneity was observed in PMT1 activity, increased membrane phospholipid methylation seems to be an important feature in pulmonary diseases where macrophages are involved.