Binding of soluble immune complexes by human monocytes and pulmonary macrophages: Effects of cigarette smoking

The Fc receptor of human monocytes and pulmonary macrophages has been evaluated quantitatively by binding of radiolabeled soluble IC. On both cell types, binding was mediated by saturable surface receptors specifically inhibited by aggregated human IgG, and IgG₃. The affinity of the Fc receptor was similar on monocytes and pulmonary macrophages from nonsmokers, but macrophages demonstrated four to 13 times more surface receptors than circulating monocytes. No difference in Fc receptor binding of monocytes was observed between cigarette smokers and nonsmokers. However, pulmonary macrophages from smokers demonstrated a significantly lower Fc receptor affinity than did those of nonsmokers, although the number of Fc receptors was the same.