Interleukin-6 receptor (IL-6R) is a receptor for IL-6, belonging to the type I cytokine receptor family, subfamily 3. IL-6 is a potent pleiotropic cytokine that regulates cell growth and differentiation and plays an important role in immune response. IL-6R is a protein complex composed of this protein and the interleukin-6 signal transductor (IL6ST/GP130/IL6β). This receptor subunit is also shared by many other cytokines. Dysproduction of IL-6 and this receptor has been implicated in the pathogenesis of many diseases, such as multiple myeloma, autoimmune diseases and prostate cancer. In addition, IL-6Rα (IL-6RA) is the primary functional alpha subunit of the IL-6 receptor, which is also a component of other interleukin receptors. IL-6RA is a type I transmembrane glycoprotein that regulates the biological activity of IL-6 by forming a complex with CD130. IL-6R also plays an important role in acute response and hematopoietic response. A binding ELISA assay was conducted to detect the association of recombinant human IL6R with recombinant human JAK2. Briefly, biotin-linked IL6R were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to JAK2-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µl stop solution to the wells and read at 450 nm immediately. The binding activity of IL6R and JAK2 was shown in Figure 1, the EC50 for this effect is 1.182 ug/mL.