Stimulation by a bacterial extract (broncho-vaxom) of the metabolic and functional activities of murine macrophages

Abstract

Peritoneal and bone marrow-derived macrophages of the C57BL/6 and DBA/2 mouse strains were exposed in vitro to increasing concentrations of the bacterial lysate Broncho-Vaxom (BV), in the presence or absence of macrophage-activating factor (MAF)-rich media. Two metabolic pathways and two functional activities of the macrophages were studied. First, oxidative metabolism was found to increase sharphy in macrophages incubated with BV, as measured by the catabolism of glucose via the hexose monophosphate shunt pathway, and by the production of the superoxide anion (O 2 −). Both effects were further increased by co-stimulation of macrophages with MAF. Second, exposure to BV together with MAF (or with recombinant murine interferon-γ) led to acquisition by macrophages of the capacity to destroy the intracellular parasite Leishmania enriettii; such activated macrophages were also lytic towards P815 mastocytoma indicator target cells. These cytotoxic properties failed to develop in the absence of MAF. The BV-dependent increase in metabolic and functional activities was of the same magnitude as that induced by incubation of macrophages with 10 ng/ml of bacterial lipopolysaccharide (LPS). Residual contamination of BV by endotoxin was however much lower. In addition, polymyxin B, a LPS inhibitor, blocked the effect of LPS without significantly affecting macrophage stimulation by BV. These experiments indicate that BV can markedly stimulate macrophage metabolic and functional parameters that are important for host defense against pathogens and tumors.