Receptor-Mediated O−2Release by Alveolar Macrophages and Peripheral Blood Monocytes from Smokers and Nonsmokers: Priming and Triggering Effects of Monomeric IgG, Concanavalin A,N-Formyl-Methionyl-Leucyl-Phenylalanine, Phorbol Myristate Acetate, and Cytochalasin D

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Abstract
Receptor-mediated superoxide (O−2) release by alveolar macrophages and peripheral blood monocytes from smokers and nonsmokers was studied in vitro. When the cells were incubated with monomeric IgG or monomelic Fc(IgG) fragment, no cell O−2 release was observed. However, when cytochalasin D (Cyto D) was subsequently added to the cell suspension, we observed a markedly enhanced O−2 release. Neither Cyto D alone nor the double stimulation of following Cyto D with monomeric IgG induced O−2 release. Concanavalin A (Con A) also had a priming effect on O2 release in combination with Cyto D, as did monomeric IgG or monomeric Fc(IgG) fragment. On the other hand, heat-aggregated IgG, N-formyl-methionyl-leucyl-phenylalanine (FMLP), or phorbol myristate acetate (PMA) induced O−2 release without the addition of Cyto D. Thus, we observed 2 different mechanisms in the receptor-mediated O−2 release by alveolar macrophages and peripheral blood monocytes. Alveolar macrophages from smokers, which had a higher affinity and a larger number of monomeric IgG binding sites per cell than those from nonsmokers, were more reactive to the double stimulation of following monomeric IgG with Cyto D than to that of Con A and Cyto D, FMLP, or PMA, but for peripheral blood monocytes it was the reverse. We conclude that the binding of monomeric IgG to the Fc(IgG) receptor of alveolar macrophages or peripheral blood monocytes results in a priming effect on the cells for O−2 release, and that the regulation of receptor-mediated O−2 release by alveolar macrophages differs at least in part from that of peripheral blood monocytes.

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