Activation of murine peritoneal macrophages by water-soluble extracts of Bursaphelenchus xylophilus, a pine wood nematode

In our previous study, water-soluble extracts from Bursaphelenchus xylophilus (B. xylophilus), a pine wood nematode, were shown to enhance interleukin (IL)-4 plus lipopolysaccharide-induced polyclonal immunoglobulin (Ig) E production in vitro in mice and to increase serum levels of an antigen-nonspecific IgE in vivo. Here we examined whether the nematode extracts stimulate immunofunctions of murine peritoneal macrophages. In both resident and inflammatory macrophages, Fcgamma receptor-mediated phagocytosis was markedly activated by B. xylophilus extracts, while non-specific phagocytosis was not. The enhancement of specific phagocytosis was accompanied by an increase in the formation of IgG-Fcgamma receptor rosettes. B. xylophilus extracts also stimulated IL-1beta 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 B. xylophilus contain an activating substance(s) for immunofunctions in macrophages, besides an enhancing factor for polyclonal IgE production.