Antibodymediated enhancement of Legionella pneumophila-induced interleukin 1 activity. Infect. Immun

The ability of antibody specific for Legionelk pneumophila to enhance the induction of interleukin 1 (IL-1) production by murine peritoneal, splenic, and pulmonary macrophages in response to the bacterium was examined. Two preparations of L. pneumophila were utilized, a formalin-kilied whole-cell preparation and viable bacteria. We measured both secreted (sIL-1) and cell membrane-associated (mIL-l) activities after incubation of the macrophages with the bacterial preparations in the presence or absence of the antibody. Both bacterial preparations induced sIL-1 and mIL-1 activities in each of the macrophage populations tested. These activities were generally enhanced by pretreating the bacteria with antibody, with the greatest enhancing activity observed for the formalin-killed preparations at lower doses of bacteria. Interleukin 1 (IL-1) is produced primarily by mononuclear phagocytes in response to a variety of stimuli, including microorganisms and microbial products as well as various synthetic chemicals (16, 17, 39). IL-1 may be detected either as a soluble protein secreted into the culture supernatant (or plasma), referred to as sIL-1 activity, or as a membrane-associated form, referred to as mIL-1 activity (32, 33). Additionally, IL-1 activity is associated with two forms of peptide, referred to as IL-1 alpha and IL-1 beta, but the two forms appear to share the same receptor and to have overlapping biologic activities (18). Immune complexes, Fc sub-fragments, and aggregated immunoglobulin are reporte