Interleukin-6. Molecular model of a molecule of the cytokine protein interleukin-6. This protein is produced in the body and has a wide variety of functions in the immune system. These include stimulating the growth and development of B-cells, the white blood cells responsible for the production of antibodies. As well as this, it plays a role in inducing nerve cell differentiation. It is also a growth factor for myelomas and plasmacytomas (white blood cell cancers). The amino acid structure of the molecule is shown in ball and stick form. The structure of the molecule is shown by red alpha helices linked by white strands.