Human alveolar macrophage subpopulations isolated on discontinuous albumin gradients. Cytological data in normals and sarcoid patients

Cells recovered by bronchoalveolar lavage (BAL) from ten subjects (five normals and five sarcoid patients) were centrifuged on discontinuous albumin gradients to study alveolar macrophage (AM) heterogeneity. The gradient was made with nine bovine albumin concentrations (from 8 to 30%). After centrifugation (4000 x g) cells were recovered from the interfaces. The majority of AM was recovered in upper and medium layers with AM purity reaching 90-100% in upper layers, while lymphocytes and granulocytes were found in lower layers. Alveolar macrophage morphology was different along the gradient. Large cytoplasmic vacuoles were found in AM from upper layers. Alveolar macrophage cytoplasmic diameters decreased from the top to the bottom of the gradient, but AM from sarcoid patients appeared larger than AM from normals. Alveolar macrophage nucleo-cytoplasmic ratios increased from top to bottom, but were lower in sarcoid patients than in normals. Alveolar macrophage peroxidase activity was rare (0.5-2% of AM) but reached a higher proportion in upper and lower layers.