CD32 is a surface receptor protein and part of a large population of B cell co-receptors, which act to modulate signaling.
It has a low-affinity for IgG antibodies and down-regulates antibody production in the presence of IgG. This feedback loops essentially lowers the production of IgG produced by B cells when there is a surplus in the body.
Monoclonal antibodies can distinguish between CD32A and CD32B.
^Coico, R., Sunshine, G., and Benjamin, E. (2003). "Immunology: A Short Course" p.97.
^Veri MC, Gorlatov S, Li H, et al. (2007). "Monoclonal antibodies capable of discriminating the human inhibitory Fcgamma-receptor IIB (CD32B) from the activating Fcgamma-receptor IIA (CD32A): biochemical, biological and functional characterization". Immunology121 (3): 392–404. doi:10.1111/j.1365-2567.2007.02588.x. PMC2265948. PMID17386079.