The eosinophil leukocyte: controversies of recruitment and function.

Eosinophil leukocytes have been studied for over 100 years, with various theories being advanced of the mechanism of their recruitment and function, especially in relation to the lesions of allergy, asthma and parasitism. Early notions of recruitment and function depended on observations of the cells in inflammatory lesions, while later theories have used additional information from in vitro studies. Many issues are still unresolved. This review aims to cover the older and more recent literature of the mechanisms of accumulation of eosinophil leukocytes and their functions, with a view to illuminating the controversies and difficulties of research in the area.