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. Author manuscript; available in PMC: 2012 Dec 30.
Published in final edited form as: Immunol Lett. 2011 Sep 6;141(1):36–44. doi: 10.1016/j.imlet.2011.08.004

Figure 2.

Figure 2

Possible interaction partners of soluble Fc-epsilon-RI (sFcεRI) in vivo. A) FcεRI exists as a membrane bound as well as a soluble isoform in human blood. In serum, sFcεRI is found as a true soluble form or as a sFcεRI-IgE complex when bound to its natural ligand. Potentially, sFcεRI-IgE complexes can interact with antigens and form immune complexes of higher order. Free sFcεRI can additionally interact with membrane IgE expressed on B cells. sFcεRI-IgE complexes cannot bind to trimeric or tetrameric FcεRI expressed on the cell surface of peripheral blood cells, because the binding site of IgE and the cellular receptor is blocked by sFcεRI in solution.

B) In tissue, all interactions described for peripheral blood in (A) are theoretically possible. It remains to be defined whether the local concentration of sFcεRI in tissue is comparable to sFcεRI serum levels. Cells migrating from the periphery blood could also serve as vehicles to transport sFcεRI into tissue.