Editing CD32 (section)

== Structure and signaling ==
CD32 is a [[type I transmembrane protein]] with a helical transmembrane region.<ref name=":0" /> Whereas the extracellular region consists of three [[immunoglobulin domain]]s (roughly 100 a.a. in length), the cytosolic region varies by subtype. CD32A and CD32C possess an [[immunoreceptor tyrosine-based activation motif]] (ITAM), while CD32B has an [[immunoreceptor tyrosine-based inhibitory motif]] (ITIM). Both motif types rely upon interactions with [[SH2 domain|SH2 domain-containing proteins]] to transduce signals upon binding to an IgG immune complex. When an ITIM is [[Phosphorylation|phosphorylated]], it activates effector proteins that dephosphorylate the downstream targets of the ITAM signal cascade, such as [[Map kinase|MAP kinases]].<ref name=":1" /><ref name=":2" />

CD32 receptors bind to the [[Antibody|lower hinge region]] of IgG via an extracellular domain. Additionally, all CD32 subtypes readily bind [[IgG1]] and [[IgG3]] immune complexes, but differ in their binding affinities for [[IgG2]] and [[IgG4]]. CD32A binds IgG2 immune complexes, but not IgG4. CD32B and CD32C bind IgG4 immune complexes, but not IgG2. The usage of [[Monoclonal antibody|monoclonal antibodies]] can distinguish between CD32A and CD32B;<ref name="pmid17386079">{{cite journal | vauthors = Veri MC, Gorlatov S, Li H, Burke S, Johnson S, Stavenhagen J, Stein KE, Bonvini E, Koenig S | display-authors = 6 | title = Monoclonal antibodies capable of discriminating the human inhibitory Fcgamma-receptor IIB (CD32B) from the activating Fcgamma-receptor IIA (CD32A): biochemical, biological and functional characterization | journal = Immunology | volume = 121 | issue = 3 | pages = 392–404 | date = July 2007 | pmid = 17386079 | pmc = 2265948 | doi = 10.1111/j.1365-2567.2007.02588.x }}</ref> however, the high degree of homology between the extracellular domains of CD32A and CD32C make differentiation difficult.