The soluble IL-6 receptor (sIL-6R) is a circulating form of the membrane-bound IL-6 receptor (IL-6R). It is generated by proteolytic cleavage of the membrane-bound receptor or by alternative splicing of IL-6R mRNA. Unlike the membrane-bound form, sIL-6R can bind to IL-6 in the absence of a cell membrane, forming a complex that can interact with the signal transducer gp130 on various cells, thereby inducing IL-6 signaling even in cells that do not express IL-6R.
