ABSTRACT
Considerable evidence has accrued to indicate that eosinophils contribute to clinical features of asthma: airway obstruction, bronchial hyperresponsiveness, and airway inflammation. Prior to learning the unique features of eosinophil biology, there was highly suggestive clinical evidence that eosinophils may have a causative association with asthma. The interest in low-density eosinophils was spurred on by a number of interesting observations. First, low-density eosinophils were increased in a number of diseases, particularly those with eosinophilia. Second, airway lavage eosinophils tended to be of low density; this suggested a phenotypic change of eosinophils in the lung and raised the possibility of an etiological link between this subpopulation and disease activity. To determine whether low-density eosinophils have increased function and therefore may reflect features of cells present in the airway, low- and normal-density eosinophils were collected from seven patients with asthma and activated with the phorbol ester phorbol myristate acetate.
