Interleukin-5, eosinophils, and disease

OSINOPHIL production can be induced in vitro by E interleukin-3 (IL-3), granulocyte-macrophage colonystimulating factor (GM-CSF), and IL-5. Both IL-3 and GM-CSF have activities on other hemopoietic lineages, whereas IL-5 is specific for the eosinophil/basophil lineage. The activity of IL-5 on basophils has been reviewed recently' and will not be discussed here. There is now good evidence that IL-5 is the major, and possibly the only, cytokine involved in the production of specific eosinophilia. Classically eosinophilia is observed in a restricted number of diseases, most notably helminth infections and allergic diseases. However, although the increase in eosinophil numbers is less spectacular, there is increasing evidence for an involvement of eosinophils in a wider spectrum of diseases.