COMMENTARY Eosinophilia, activated eosinophils and human schistosomiasis

Eosinophils are proinflammatory cells that are associated with both allergic diseases and parasitic infections. In parasitic infections the eosinophil appears to be protective, but in allergic conditions eosinophil products are damaging and contribute to the tissue pathology of the disease. A particular property of eosinophils is that they can, like macrophages, exist in different states of activation. This has important consequences for the eosinophil in both its protective and pathological roles. In this commentary we concentrate on the positive functions of eosinophil in its potentially protective role against helminth infections.