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Eosinophils and immunity to parasites

1980; Oxford University Press; Volume: 74; Linguagem: Inglês

10.1016/0035-9203(80)90271-0

1878-3503

A Butterworth,

Parasite Biology and Host Interactions

Although the association between eosinophils and helminth infections has been recognized for many years, it is only recently that attempts have been made to test for a role for the eosinophil in immunity against helminths. Much of the evidence for such a role has come from studies in vitro on the interaction between eosinophils and the larval stages of several helminths, especially schistosomes, and progress has recently been made towards an understanding of the mechanism of this interaction. Normal human eosinophils show a selective capacity, in comparison with other cell types that bear Fc receptors for bound IgG, to adhere and cause microscopically detectable damage to schistosomula of Schistosoma mansoni in the presence of human antibody. Adherence and damage is associated with degranulation of the attached cell and with the release of granule contents on the surface of the organism. The released granule contents, especially the characteristic major basic protein, both act as a ligand, promoting and maintaining eosinophil adherence, and cause direct damage to the parasite. The eosinophil may thus be regarded as a specialized cell, one of whose particular functional attributes is the ability to degranulate upon contact with large, non-phagocytosable, antibody-coated particles such as tissue-stage helminths. Other features of the interaction between eosinophils and helminths are also becoming clearer. Eosinophils can damage other helminth larvae, although the relative efficiency of eosinophils and neutrophils in some of these reactions is still controversial. The presence of complement accentuates eosinophil-mediated damage, and eosinophils which are "activated", either by mast cell mediators or in conditions of eosinophilia, show an enhanced capacity to induce damage. The most important problem still unresolved is that, although eosinophils have been shown to be involved in helminth immunity in vivo in experimental animals, evidence for their role in immunity in man is still lacking. Although clinical studies of immunity are difficult to design, such studies are now badly needed.