Gastrointestinal nematodes, trace elements, and immunity

The exploration of the scientific literature on the interrelationship among trace elements, gastrointestinal nematodes, and their requisite Th2 immunity demonstrates extensive literature but regrettably, research remains inadequate and sparse, with far fewer studies having investigated the interrelationship among trace elements and host immunity in infected hosts. Gastrointestinal nematodes, such as hookworms, Ascaris lumbricoides, and Trichuris trichiura, require activation of the Th2 arm of the immune cascade and the expression of the Th2 cytokines (interleukin-4, interleukin-5, and interleukin-10) and their effectors for worm expulsion. However, parasites have evolved a series of strategies to invade the host and to evade host defense mechanisms. Many of these mechanisms involve metalloproteinases for tissue invasion and enzymes, such as catalase and superoxide dismutase, to minimize free radical damage to the parasitic tissues from the host's immune system. Deficiencies of iron, molybdenum, copper, and zinc, have been associated with higher worm burdens, as have excessive intakes of molybdenum, iron, and copper. The possibility is emerging that there may be an optimum trace element level in the diet above which and below which the parasite is advantaged. Moreover, there is some data to suggest that specific trace elements may be directly toxic to the parasite.