The low-affinity receptors for the Fe portion of IgC (Fc gamma R) are
expressed on most of the cells of the immune system. They bind immune
complexes but not monomeric IgC. These receptors are a family of surfa
ce glycoproteins tells with homologous extrac lar domains and differen
t transmembrane and cytoplasmic portion. They mediate the biological a
ctivities of antibodies bound at the surface of all the immune cells:
Fc gamma Rs activate macrophages, neutrophils and NK cells, participat
ing in antibody-dependent cellular cytotoxicity; Fc gamma Rs activate
mast cells, resulting in the release of inflammation mediators and the
induction of cytokines; in B cells, on the contrary, cross-linking of
Fc gamma R and IgM blocks cellular activation, inhibiting Ige product
ion. Fc gamma Rs are also involved in ligand internalization and the c
learing of immune complexes.