Neutrophils express two low affinity receptors (from the Fc family) for IgG. These are CD32 and CD16.
CD16 is FcRIIIb.
Stimulated neutrophils shed CD16. The shedding may be due to the effect of a matrix metalloproteinase. However, shedding of CD16 is inhibited by both matrix metalloproteinase inhibitors and serine protease inhibitors.
There are two well described alleles of CD16, these are NA1 and NA2. Individuals who are homozygous for the NA2 allele (NA2/NA2) show less efficient phagocytosis of opsonized microorganisms.