Eosinophils and Trichinella infection: toxic for the parasite and the host?

Peripheral blood and tissue eosinophilia characterize trichinellosis in humans, and present in addition to the increased total IgE levels that occur in many helminth infections. Both processes are the consequence of T-helper 2 activation. Blood and tissue eosinophilia begins with eosinophilopoiesis in the bone marrow, which is followed by the migration of eosinophils through the circulatory system, the eosinophil infiltration of tissues at the inflammatory foci and, finally, degranulation and cell death. Recently, some aspects of eosinophilia caused by Trichinella spiralis infection have been elucidated; however, the protective role of this population of cells against Trichinella parasites remains controversial. Furthermore, when eosinophils are numerous, they can be toxic for host tissues. This review discusses these issues in both human and rodent infection models.