ENERGY RESTRICTION AND ZINC-DEFICIENCY IMPAIR THE FUNCTIONS OF MURINET-CELLS AND ANTIGEN-PRESENTING CELLS DURING GASTROINTESTINAL NEMATODEINFECTION

This study examined whether the impaired immune responses in zinc defi cient- and/or energy-restricted mice exposed to a challenge infection of Heligmosomoides polygyrus might be associated with reduced numbers of spleen cells, altered proportions of spleen cell subpopulations and /or altered function of the T cells or antigen-presenting cells (APC). Female BALB/c mice were given free access to either a zinc-sufficient (60 mg zinc/kg diet, Zn+) or a zinc-deficient diet (0.75 mg zinc/kg d iet, Zn-) or were pair-fed (PF) the zinc-sufficient diet Significant d ifferences in parasite burdens were observed, Worm numbers were lowest in Zn+ mice, intermediate in the PF mice and highest in the Zn-mice, showing that both zinc deficiency and energy restriction reduced prote ctive immunity against the gastrointestinal nematode H. polygyrus. Alt hough the absolute numbers of spleen cells were reduced in both Zn- an d energy-restricted (PF) mice, neither deficiency altered the phenotyp ic distribution of the subpopulations oi positive marker cells in the spleen. In vitro functional assays using a 1:1 ratio al APC:T cells sh owed that T-cell proliferation in response to parasite antigen (Ag) wa s impaired by a dietary effect of zinc deficiency on T cells and of en ergy restriction and zinc deficiency on APC function. Consequences of the nutritional deficiencies on cytokine production in response to par asite antigen were move complex: zinc deficiency reduced T-cell functi on [interleukin-4 and interleukin-5 (IL-4 and IL-5) production], and b oth nutritional deficits depressed APC functions [IL-4, IL-5, and inte rferon-gamma (IFN-gamma) production] and T-cell function (IFN-gamma pr oduction). Thus, this study showed that zinc deficiency and energy res triction played identifiably distinct roles in regulating host immune responses against the gastrointestinal nematode H. polygyrus.