IMMUNOLOGY OF HUMAN HELMINTH INFECTION

Parasitic helminths cause enormous morbidity among humans especially i n developing countries. These large extracellular organisms have compl ex life cycles frequently involving an arthropod vector. Helminth para sites can be tissue dwelling or intestinal but all induce a dramatic e xpansion of the Th2 lymphocyte subset. It remains unclear whether thes e Th2-derived responses, including IgE, eosinophilia and mastocytosis are important in the protective immune response to the parasite, or ar e responsible for immune-mediated pathology, or both. Interestingly, d espite high levels of IgE and other features of Th2 cell activation, a llergic responses are rarely observed in infected individuals. Helmint hs can survive for years in the infected host, and have evolved elabor ate immune evasion strategies to establish these long-lived infections including the induction of tolerance to parasite antigens. This revie w discusses the dynamics of infection with helminth parasites with spe cific emphasis on Th2 subset activation. The current knowledge of immu ne effector mechanisms, immunopathology and hopes for vaccine developm ent are also discussed.