The role of interleukin-1 in hematopoiesis.

The polypeptide interleukin 1 (IL-1) is the primary mediator of the acute-phase response and is responsible for many changes that are associated with the onset of infection. It induces fever and has profound endocrinologic metabolic and hematologic effects. Two structurally related forms of IL-1 have been described, termed IL-1 alpha and IL-1 beta. Both forms of IL-1 bind to a common receptor that is present on a variety of target cells. Recently, IL-1 has been recognized as a molecule that is important in the regulation of hematopoiesis. IL-1 induces the production of several different hematopoietic growth factors including granulocyte-macrophage, granulocyte and macrophage colony-stimulating factors and interleukin 6 by a variety of accessory cells. In addition, IL-1 acts synergistically with colony-stimulating factors in the proliferation of primitive hematopoietic progenitor cells. In vivo, the administration of IL-1 accelerates hematopoietic reconstitution after chemotherapy or radiation induced myelosuppression. In untreated animals, IL-1 may induce a shift of hematopoietic progenitor cells into the peripheral blood, and these cells may be used to repopulate the bone marrow of lethally irradiated recipients. These studies suggest that IL-1 may be used as a therapeutic agent to accelerate bone marrow recovery after myelosuppression.