Zinc deficiency impairs immune responses against parasitic nematode infections at intestinal and systemic sites

Research on the complex interactions among host nutritional status, parasitic infection and immune responsiveness has focused on the detrimental consequences of parasitic infections on host nutritional status and on mechanisms by which malnutrition impairs immunocompetence. Curiously, relatively few studies have examined the effects of malnutrition on the immune response in the parasite-infected host, and even fewer have considered the events occurring at the intestinal level, where absorption of nutrients occurs, intestinal parasites reside, and the gastrointestinal-associated lymphoid tissues play a role in directing both the local and the more systemic immune responses. Our work using a zinc-deficient nematode-infected mouse model reveals that parasites are better able to survive in the zinc-deficient hosts than in well-nourished hosts; that the production of interleukin-4 in the spleen of zinc-deficient mice is depressed, leading to depressed levels of IgE, IgG(1) and eosinophils; and that the function of T cells and antigen-presenting cells is impaired by zinc deficiency as well as by energy restriction. Given the paramount role of the gastrointestinal-associated lymphoid tissues in inducing and regulating immune responses to intestinal parasites and in orchestrating responses in the spleen and peripheral circulation, we conclude that zinc deficiency (in association with energy restriction) exerts profound effects on the gut mucosal immune system, leading to changes in systemically disseminated immune responses and, importantly, to prolonged parasite survival.