Interleukin-6 is an important cytokine involved in the immune response. IL-6 can interact with immune cells by binding to soluble or membrane bound receptors to elicit a response. It has been found that the result of IL-6 binding varies between these two types of receptor, with membrane receptor interaction having a protective response, and the binding of soluble receptors is pro-inflammatory .
 Schaper, F. and Rose-John, S. (2015). Interleukin-6: Biology, signalling and strategies of blockade. Cytokine & Growth Factor Reviews, 26(5), pp.475-487.