Cytokines and their receptors: molecular mechanism of interleukin-6 gene repression by glucocorticoids.

Recent years have seen the discovery and molecular characterization of a bewildering array of cytokines and hematopoietic growth factors--and an even more complex description of their overlapping functions. The molecular cloning of a wide array of the cell-surface receptors for these cytokines has led to the recognition of classes of structurally related receptor superfamilies. The functional receptors for many of these cytokines (e.g., interleukin (IL)-2R and IL-6R) involve two distinct subunits; strikingly, the same beta subunit can interact with distinct alpha subunits to constitute the receptor for different cytokines (e.g., those for IL-3, IL-5, and granulocyte monocyte colony-stimulating factor). Considerable progress has also been made in defining the molecular mechanisms that underlie clinically relevant cytokine-related phenomena. As an example, the molecular mechanism by which glucocorticoids inhibit IL-6 gene expression has been shown to include the occlusion of the inducible enhancer and the basal promoter elements in the IL-6 promoter. Acute rejection episodes in renal transplant patients are accompanied by increases in serum IL-6 levels; the administration of glucocorticoids during these episodes leads to a rapid and marked decrease in IL-6 levels. It appears that the serum IL-6 level may be a useful diagnostic and prognostic indicator in the transplant patient.