Three distinct, but closely related classes of receptors that bind the Fc portion of IgG have been identified (Fcgamma RI, II and III). The FcgammaRI family consists of three closely related genes termed A, B, and C. This gene likely encodes a non-functional protein that is not detectable at the cell surface and binds ligand with low affinity. [provided by RefSeq, Nov 2019] see less Three distinct, but closely related classes of receptors that bind the Fc portion of IgG have been identified (Fcgamma RI, II and III). The FcgammaRI family consists of three closely related genes termed A, B, and C. This gene likely encodes a non-functional protein that is not detectable at the cell surface and binds ligand with low affinity. [provided by RefSeq, Nov 2019]