Interleukin-6 (IL-6) is a multifunctional protein originally discovered in the media of cells stimulated with double stranded RNA. IL-6 appears to be directly involved in the responses that occur after infection and injury and may prove to be as important as IL-1 and TNF-α in regulating the acute phase response. IL-6 is reported to be produced by fibroblasts, activated T cells, activated monocytes or macrophages, and endothelial cells. It acts upon a variety of cells, including fibroblasts, myeloid progenitor cells, T cells, B cells and hepatocytes. IL-6 induces multiple effects, as indicated by its numerous synonyms: plasmacytoma growth factor (PCT-GF), interferon-β-2 (IFN-β2), monocyte derived human B cell growth factor, B cell stimulating factor (BSF-2), hepatocyte stimulating factor (HSF), Interleukin Hybridoma/Plasmacytoma-1 (IL-HP1). In addition, IL-6 appears to interact with IL-2 in the proliferation of T lymphocytes. IL-6 also potentiates the proliferative effect of IL-3 on multipotential hematopoietic progenitors.
