Expression of the Adhesion Molecule ICAM-1 on Alveolar Macrophages and in Serum in Extrinsic Allergic Alveolitis

ICAM-1 expression was studied on alveolar macrophages (AM) in extrinsic allergic alveolitis (EAA) using immunocytochemistry and cytometry. Compared to control donors, EAA patients had higher percentages of ICAM-1+ AM (75% vs. 30%) and the antigen density was more than sixfold higher (673 vs. 103 channels). Levels of soluble serum ICAM-1 were found increased in EAA patients with an average of 866.2 +/- 300 ng/ml versus 394.8 +/- 110 ng/ml in controls. These data are consistent with the concept that antigen contact upregulates ICAM-1 expression on AM in EAA followed by shedding and an increase in serum sICAM-1.