[Mechanism of parasite killing by eosinophils in parasitic infections]

Eosinophils kill a variety of helminth parasites and some protozoan parasites in vitro by antibody- or complement-dependent mechanisms. Nevertheless, direct evidence of in vivo parasite killing by eosinophils is scanty. In Angiostrongylus cantonensis infection in non-permissive hosts, however, the intracranial worms are killed by eosinophils in the cerebrospinal fluid, indicating that the cells are associated, not only with the protective immunity against helminthic infections, but also with the innate resistance of the non-permissive host. Moreover, eosinophils could be probably involved in the damage of host tissues, e.g., loss of Purkinje cells in the cerebellum of mice infected with A. cantonensis. A variety of basic proteins derived from eosinophil granules, such as MBP, ECP, EDN (= EPX) and EPO, and possibly active oxygen products, may be involved in the killing of parasites.