Activation of Murine Peritoneal Macrophages by Water-Soluble Extracts of Bursaphelenchus xylophilus, a Pine Wood Nematode

In our previous study, water-soluble extracts from <I>Bursaphelenchus xylophilus</I> (<I>B. xylophilus</I>), a pine wood nematode, were shown to enhance interleukin (IL)-4 plus lipopolysaccharide-induced polyclonal immunoglobulin (Ig) E production <I>in vitro</I> in mice and to increase serum levels of an antigen-nonspecific IgE <I>in vivo</I>. Here we examined whether the nematode extracts stimulate immunofunctions of murine peritoneal macrophages. In both resident and inflammatory macrophages, Fcγ receptor-mediated phagocytosis was markedly activated by <I>B. xylophilus</I> extracts, while non-specific phagocytosis was not. The enhancement of specific phagocytosis was accompanied by an increase in the formation of IgG-Fcγ receptor rosettes. <I>B. xylophilus</I> extracts also stimulated IL-1β production in both types of macrophages, and enhanced NO production and mRNA expression of inflammatory cytokines in inflammatory macrophages. These results indicate that the extracts of <I>B. xylophilus</I> contain an activating substance(s) for immunofunctions in macrophages, besides an enhancing factor for polyclonal IgE production.