- Receptor recognition sites of cytokines are organized as exchangeable modules. Transfer of the leukemia inhibitory factor receptor-binding site from ciliary neurotrophic factor to interleukin-6. Kallen, K.J., Grötzinger, J., Lelièvre, E., Vollmer, P., Aasland, D., Renné, C., Müllberg, J., Myer zum Büschenfelde, K.H., Gascan, H., Rose-John, S. J. Biol. Chem. (1999)