The protective activity of immunostimulants against Listeria monocytogenes infection in mice

Abstract

The function of peritoneal macrophages induced by intraperitoneal (i.p.) injection of attenuated Streptococcus pyogenes (OK-432), Bacillus Calmette Guérin (BCG), protein-bound polysaccharide preparation isolated from Coriolus vesicolor (PSK) or Lactobacillus casei was examined. The PMA-triggered respiratory burst (production of O2- and H2O2) of macrophages induced by OK-432, BCG or Lac. casei was greater than that of resident or thioglycollate-stimulated macrophages and was similar to that of BCG-activated macrophages. PSK failed to enhance the production of O2- or H2O2 by macrophages. Alkaline phosphodiesterase (APD) activity was reduced in macrophages induced by OK-432, BCG or Lac. casei injection and in BCG-activated macrophages. The APD activity of macrophages obtained 7 and 13 days after i.p. injection of PSK was elevated, as with thioglycollate-stimulated macrophages. Listericidal activity in vitro was enhanced in macrophages obtained in 13 and 7 days, but suppressed in macrophages obtained 2 days after OK-432, BCG or Lac. casei injection. Lac. casei administered either 2 or 13 days before infection with Listeria monocytogenes was protective but OK-432, BCG (0.1 mg) and PSK were not, even though they were able to stimulate macrophage function.