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Cytokines and Receptors

R&D Systems offers a wide selection of tools to study cytokines, chemokines, and their receptors. These include active proteins, antibodies, ELISAs, Multiplex Assays, Primers, and more.

What are cytokines? Cytokine is a term used to describe a broad range of structurally diverse molecular families and individual proteins best known for their many roles in immune system function. They are often pleiotropic molecules with diverse and cell type specific activities. Cytokine functions are mediated by binding specific receptors and their activities include regulating cell activation, hematopoiesis, apoptosis, cell migration, and cell proliferation. In this capacity, they are involved in virtually all aspects of both innate and adaptive immune responses. Leukocytes are a primary source of cytokines, although they may be produced by many other cell types as well.

Structural analysis of the many different cytokines has allowed for classification based on similarity into several large families. Three common families are the four-helix bundle cytokines, the TNF superfamily cytokines, and the TGF-beta family. The helical cytokine family is characterized by a four alpha helix bundle and further divided into short and long chain cytokines. Popular members of the short-chain four-helix bundle family include IL-2, IL-4, IL-7, IL-15, GM-CSF, M-CSF, and SCF. The long-chain four-helix bundle cytokines include thrombopoietin (TPO), erythropoietin (EPO), growth hormone, IL-6, IL-11, Oncostatin M, LIF, and G-CSF. Next, the TNF superfamily includes TNF alpha, Lymphotoxin alpha, Lymphotoxin beta, CD40 ligand, and 4-1BB ligand. Finally, the TGF-beta family includes several notable members TGF-beta, the bone morphogenetic proteins (BMPs), the growth differentiation factors (GDFs), and the activin and inhibin subfamilies.

Cytokine receptors are cell-surface glycoproteins that provide docking sites for cytokines and relay signals inside the cell. Several exist as both soluble and membrane-bound forms. Like their cytokine counterparts, receptors are categorized by family. The main families include Type I cytokine receptors, type II cytokine receptors, TNF receptor superfamily, TGF-beta receptor family, chemokine receptors, and the Ig superfamily.