REGULATION OF INTERLEUKIN-5 AND GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR EXPRESSION

This review concerns the regulation of expression of the two main eosi nophil differentiating factors, interleukin-5 (IL-5) and granulocyte-m acrophage colony-stimulating factor (GM-CSF). The latter, GM-CSF, is e xpressed in a wide variety of differentiated and non-differentiated ce ll types: T cells, monocytes, macrophages, fibroblasts, and endothelia l cells. On the other hand, IL-5 is only expressed by a limited number of fully differentiated cells: eosinophils, mast cells, and a subset of T cells. Activation of GM-CSF in T cells and non-T cells occurs by different mechanisms, regulated both transcriptionally and post-transc riptionally. The transcriptional activation of GM-CSF via protein kina se C pathway and via viral transactivating proteins involves different regulatory elements of its promoter. Although one of these cis acting elements is common to IL-5, the activation of IL-5 apparently proceed s via different mechanism(s).