The role of interleukin-6 in development.

Interleukin-6 is a member of a class of hormone-like molecules termed cytokines. The actions of IL-6 are highly pleiotropic. In adults IL-6 functions as a major mediator of inflammatory responses as well as inducing the synthesis of acute phase proteins by the liver following infection or injury. Based on in vitro and in vivo studies IL-6 also has important functions in regulating the development of multiple lineages of hemopoietic cells. It may also be an inflammatory mediator in the central nervous system. Although IL-6 has been found in early mouse embryos, its function has not yet been determined. Its expression by placental trophoblasts and maternal decidua suggests that it has some role in fetal-maternal interactions. Finally, the response of fetal hemopoietic progenitor cells to IL-6 suggests that IL-6 may have a broader action on the expansion and maturation of fetal precursors. New approaches such as those involving the disruption of the IL-6 gene in mice will be needed for a more complete understanding of IL-6's role in embryonic development.