Experts from a variety of areas compare and discuss IL-6 and LIF in order to provide a new understanding of their modes of action, the significance of their polyfunctionalization—why the body chooses to use one molecule to regulate various cell types—and their functional overlap. Covers such topics as actions of IL-6 and LIF on lymphoid populations, on megakaryocyte and platelet production, on bone metabolism, their effects on leukemic cells and much more. Includes contributions from researchers working on a variety of cell types and organ systems along with potential clinical applications regarding these two factors.