Human eosinophil isolation and the measurement of apoptosis

Eosinophils have been implicated in allergic diseases, such as bronchial asthma, which is characterized by elevated eosinophil numbers in the bronchoalveolar lavage fluid and peripheral blood. Their accumulation and activation within the airway mucosa is thought to cause tissue injury, contraction of airway smooth muscle, and increased bronchial responsiveness (1-3). The balance between cell maturation and death is of great importance in determining the number of eosinophils in the blood and tissues (4-6). Following in vitro culture in the absence of cytokines, eosinophils undergo apoptosis, or programmed cell death (7,8), a process that can be inhibited by cytokines such as interleukin-3 and -5 and granulocyte-macrophage colony-stimulating factor (GM-CSF), and accelerated by such factors as corticosteroids and Fas (7-11).