THE BIOLOGICAL ROLE OF INTERLEUKIN-5

Eosinophilia can be a specific cellular response, but the mechanisms of its control are not yet fully understood. Interleukin 5 (IL‐5) is a lineage‐specific eosinophil differentiation and activation factor. It can be detected in the serum of mice with eosinophilia, and antibody to IL‐5 blocks the development of parasite‐induced eosinophilia. The role of other cytokines in the production of eosinophil precursors is not clear, and may be in vitro artifacts. The biological significance of the B cell growth factor (BCGF) activity of murine IL‐5 remains a puzzle. Although eosinophilia is often associated with high levels of IgE antibody, IL‐5 appears not to be involved in this response, where interleukin 4 appears to be the main controlling factor. Understanding this activity has been made more difficult, since human IL‐5 has no activity in analogous human BCGF assays. A better understanding of the role of these activities will probably come from studies in vivo rather than from cell culture. Copyright © 1990 AlphaMed Press