Normal Human Alveolar Macrophages Have More Ability than Blood Monocytes to Produce Cell-associated Interleukin-1-alpha

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Abstract
Human alveolar macrophages (AM) were obtained by bronchoalveolar lavage from healthy donors, and their abilities to produce extracellular and cell-associated interleukin 1 (IL-1) in response to various activation stimuli were compared with those of autologous blood monocytes. The production of IL-1 alpha and IL-1 beta by monocytes and AM was examined by thymocyte co-stimulation assay and enzyme immunoassays (EIA). Results showed that when activated with lipopolysaccharide (LPS) or desmethyl muramyl dipeptide (norMDP), AM released much less extracellular IL-1 beta than did blood monocytes. In contrast, these activated AM produced more cell-associated IL-1 than did blood monocytes. When the IL-1 activity was examined by the thymocyte assay, the extracellular and cell-associated IL-1 produced by the two cell types were largely IL-1 beta and IL-1 alpha, respectively, as shown by antibody neutralization. The cell-associated IL-1 activity of AM induced by the synergistic actions of suboptimal concentrations of recombinant interferon-gamma (rIFN-gamma) and norMDP was also higher than that of autologous blood monocytes. Consistent with these findings on AM, macrophages generated in vitro by maturation of blood monocytes produced higher levels of cell-associated IL-1 activity than did freshly isolated monocytes. These observations suggest that AM may play a critical role in situ regulation of pulmonary inflammatory and immune reactions through production of cell-associated IL-1 alpha.