Interleukin-6 (IL-6) molecular structure, computer artwork. This is a protein of the immune system. The amino acid structure is shown in stick and ball form, while the molecular structure is shown by the orange alpha helices. Interleukins are signalling molecules released by cells to affect the behaviour of other cells. IL-6 is released by a number of white blood cells. It has a number of functions in the immune system as well as affecting other cells of the body. IL-6 stimulates the differentiation of B-cells, allowing them to produce specific antibodies, as well as inducing nerve cell differentiation. IL-6 is also a growth factor for the white blood cell cancers myeloma and plasmacytoma.