The destruction of virulent Entamoeba histolytica by activated human eosinophils

Abstract

Unlike normal (i.e., non-activated) human eosinophils that are unable to destroy virulent Entamoeba histolytica even in the presence of antibodies and complement, activated eosinophils effectively destroy the parasite in vitro without the help of opsonins, yet increase this capacity with their assistance. Many activated eosinophils succumb in the process as well, probably victims of toxic products released by dying amoebae. Human activated eosinophils thus behave more like activated macrophages than like neutrophil polymorphonuclear leucocytes that are notoriously incompetent in dealing with virulent amoebae. As a regular constituent of early inflammatory reactions, and notwithstanding the absence of blood and tissue eosinophilia in invasive amoebiasis, the activated eosinophil may play a role in the defence against E. histolytica.

Ups and Downs of Mucosal Cellular Immunity against Protozoan Parasites

“…Early studies using T. gondii have demonstrated that IgE-bearing eosinophil can be cytotoxic (79). Regarding E. histolytica infection, in vitro data suggest that unlike normal human eosinophils which are destroyed, eosinophils which have been activated by complement and armed with specific IgE antibodies effectively destroy virulent E. histolytica (58). Unfortunately, the clinical relevance of this finding is uncertain since amoebic colitis does not appear to be associated with intestinal eosinophilia.…”

Does the eosinophil have a protective role in amebiasis?

“…Moreover, axenically grown trophozoites of E. histolytica kill in vitro normal human neutrophils and eosinophils (not-withstanding the aid by antibody and complement), normal monocytes and lymphocytes, without suffering changes in their own viability (Jarumilinta & Kradolfer 1964, Artigas et al 1966, Guerrant et al 1981, Salata et al 1985, 1987, López-Osuna et al 1986, López-Osuna & Kretschmer 1989 fectively destroying virulent amebas, even though finally succumbing in the process as well (Salata et al 1985). In our laboratory we found that the same occurs with activated human peripheral blood eosinophils (López-Osuna et al 1992). …”

Eosinophils, HLA and amebic disease

“…In contrast, activated eosinophils turned out to be quite efficient in destroying the parasite, although ultimately succumbing in the process as well. They now resembled the performance of human activated macrophages, except that anti-amebic antibodies clearly enhanced the amebolytic effect of eosinophils, but not that of macrophages [4]. We then turned our attention to an in vivo model to evaluate the possible rote of eosinophils in invasive amebiasis.…”