IL6 mediates its biological effects through the type I IL6 receptor system that consists of two chains, IL6Ra and gp130. The IL6Ra chain is the binding component specific to IL6, while the gp130 only transmits signals of IL6 when bound to IL6Ra. The gp130 also can transmit signals from LIF, OSM, CNTF, IL11 and CT-1 in conjunction with other receptor subunits. The low-affinity binding site for IL6 is composed of IL6Ra alone. IL6Ra is expressed in a wide range of cells including T cells, fibroblasts and macrophages. Soluble IL6Ra which consists of only the extracellular domain of the IL6Ra chain, acts as an agonist of IL6 activity at low concentrations. Alternative Names: B cell stimulatory factor-2 protein, soluble IL-6 receptor alpha protein, IL-6, IL6, Interleukin 6R alpha protein, CD126 protein, IL-6R alpha protein, IL-6 protein, IL 6 protein, IL 6