Susceptibility of HRS/J mice to listeriosis: macrophage activity

Abstract

Macrophage functions, including phagocytosis and bactericidal and oxidative activities, were measured in highly susceptible Listeria monocytogenes-sensitive HRS/J homozygous and heterozygous mice. Phagocytic studies with both caseinate-elicited and L. monocytogenes-immune macrophages revealed comparable engulfment of latex particles, zymosan, and bacteria by mononuclear phagocytes obtained from all experimental mouse strains. Elicited macrophages cultivated from mutant hairless and heterozygous littermates exhibited a reduced capacity to control Listeria infection compared with cells derived from CD-1 mice. However, intracellular killing of the microorganisms by immune macrophages was comparable to that observed with the outbred controls. Studies on oxidative metabolic activities associated with the respiratory burst indicate that while intracellular nitroblue tetrazolium reduction was comparable for macrophages cultivated from all mouse strains, the liberation of superoxide anion and chemiluminescence responses were significantly diminished in caseinate-elicited HRS/J cells. Moreover, immune elicited hr/hr and hr/+ macrophages generated oxidative species at levels comparable to that observed with cells derived from resistant animals. Thus, immunologically elicited HRS/J mice are capable of responding to sublethal Listeria infection with heightened antibacterial and oxidative activities.