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. Author manuscript; available in PMC: 2011 Jul 20.
Published in final edited form as: Eur J Immunol. 2007 Nov;37(Suppl 1):S34–S45. doi: 10.1002/eji.200737772

Figure 2.

Figure 2

Four examples of cytokines and their receptors. A. TNF. TNFα is biologically active as a trimer. The TNF receptor is comprised of three chains (homotrimer) of either the TNF type 1 receptor (TNF-RI, also known as p55) [34] or a homotrimer of the type 2 receptor, not shown (also known as p75) [34] and initiates signal transduction. The cytoplasmic domains of the TNF R (I or II) contains death domains. B. IL-1. IL-1 binds to the type I IL-1 receptor (ligand binding chain) with a low affinity [7]. The IL-1 receptor accessory protein (IL-1RAcP) [44] is then recruited to form a high affinity heterodimer. The cytoplasmic domains of the IL-1 receptors (type I and IL-1RAcP) contain the Toll-IL-1 receptor (TIR) domains, which are essential for signaling [45]. The cytoplasmic domains of the IL-1 receptors share a high level of homology with the TLR and signaling is also similar. C. IL-2. IL-2 binds to the IL-2Rα chain with a low affinity [46, 47]. The signaling chain IL-2Rβ forms the dimeric complex. D. IL-6. Like IL-1 and TNF, IL-6 is a pleiotropic cytokine [48]. IL-6 first binds to the soluble IL-6 receptor. The soluble IL-6 receptor binds to two chains of the gp130 receptor initiating a signal.