Expression of Fc receptors is suppressed in alveolar macrophages from patients with sarcoidosis.

To study the expression of Fc receptors in human alveolar macrophages (AM), the cells were collected from 12 healthy controls and 22 patients with sarcoidosis and the activity involved in binding to 125I-soluble immune complexes (IC) was investigated. The binding of 125I-IC was significantly suppressed in cells from the patients. A Scatchard plot analysis revealed that this suppression was due to a reduction in the number of Fc receptors on the surface membrane and not the result of a decrease in the binding affinity of the receptors. Rosette formation was observed by incubating AM with antibody-coated ox red blood cells. The presence of rosette forming cells was about 70% in the AM from healthy controls, while, a rate of only 50% was seen in those with sarcoidosis. These results indicate that the decrease of the 125I-IC binding in the AM from patients with sarcoidosis is to some extent the result of an increase in the population of the Fc receptor negative macrophages.