CD32 (cluster of differentiation 32), also known as FcγRII or FCGR2, is a surface receptor glycoprotein belonging to the Ig gene superfamily.
Both motif types rely upon interactions with SH2 domain-containing proteins to transduce signals upon binding to an IgG immune complex.
When an ITIM is phosphorylated, it activates effector proteins that dephosphorylate the downstream targets of the ITAM signal cascade, such as MAP kinases.
The usage of monoclonal antibodies can distinguish between CD32A and CD32B;[6] however, the high degree of homology between the extracellular domains of CD32A and CD32C make differentiation difficult.
[4] CD32A also plays an important role in platelet activation, adhesion, and aggregation in response to injured blood vessels.
[3] When bound to an IgG immune complex, the cytosolic ITAM can promote phagocytic activity and cytokine secretion in neutrophils and macrophages.
[3] CD32B is an inhibitory surface receptor that is part of a large population of B cell co-receptors, which act to modulate signaling.
[3] Some individuals inheriting mutated, inactivate CD32B genes have a reduced risk of contracting malaria; this is attributed to an enhancement of FcR-dependent phagocytic functions.
Likewise, systemic lupus erythematosus (SLE) in humans is associated with a decrease in CD32B on the surface of memory B cells.