The eosinophil

There is controversy on functions, ranging from protective, tissue protecting to aggressive tissue damaging effects. High numbers are found in many diseases. The cell is invariably seen when helminths invade tissues, with numbers correlated with IgE titres and it is the major cytotoxic cell for parasitic larvae. It is produced by bone marrow, and controlled by T cell products and other mediators. A fundamental connection exists between asthma and eosinophils irrespective of the presence of an allergic factor. Study of sputum samples is of more value than blood eosinophil numbers. After allergen challenge there may be both immediate and late reactions. Where the late reaction occurs blood eosinophil numbers rise, indicating a central position in the pathogenesis. Cellular proteins and extracellular products and their effects are tabulated. The cells are heterogenous into two types, normodense (low activity) and hypodense which have high activity of increased secretory activity, chemotactic response etc. Treatments for asthma and beta-2-agonists and corticosteroids inhibit mediator release and eosinophil numbers and the abnormality should be considered early.