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.