Hematologic effects of interleukin-1 and interleukin-6.

Interleukin-1 and interleukin-6 are two of a great number of cytokines involved in the synergistic regulation of hematopoietic progenitor cell growth. Clinical descriptions that suggest several therapeutic uses for interleukin-1 and interleukin-6 have appeared. In either high-dose chemotherapy or bone marrow transplantation, either cytokine can be myeloprotective or myelorestorative and can increase platelet recovery. Also, both cytokines could be useful in stimulating the peripheralization of stem-progenitor cells in vivo. In vitro, both cytokines have proven useful in the ex vivo expansion of hematopoietic progenitor cells and subsequent reinfusion in patients undergoing autologous bone marrow transplantation. Mechanistically, both stimulate production of other regulators of hematopoiesis, induce increased cell surface expression of receptors for hematopoietic growth factors, and shorten the cell cycle transit time of progenitors. Differences in the actions of interleukin-6 and interleukin-1 on highly enriched and purified stem cells are starting to emerge, with proliferation in stem cell factor and interleukin-6 preserving marrow-repopulating ability of stem cells, and the proliferative stimulus of stem cell factor and interleukin-1 leading to more rapid differentiation.