An antibody digested by papain yields three<unk> s, two Fab<unk> s and one Fc<unk>  An antibody digested by pepsin yields two<unk> s: a F(ab')2<unk>  and a pFc'<unk>  The<unk>  (Fc<unk>  is the tail<unk>  of an antibody that interacts with cell surface receptors called Fc receptors and some proteins of the complement system. This property allows antibodies to activate the immune system. In IgG, IgA and IgD antibody isotypes, the Fc<unk>  is composed of two identical protein<unk> s, derived from the second and third constant domains of the antibody's two heavy chains; IgM and IgE Fc<unk> s contain three heavy chain constant domains (CH domains 2–4) in each polypeptide chain. The Fc<unk> s of IgGs bear a highly conserved N-glycosylation site. Glycosylation of the Fc<unk>  is essential for Fc receptor-mediated activity. The N-glycans attached to this site are predominantly core-fucosylated diantennary structures of the complex type. In addition, small amounts of these N-glycans also bear bisecting GlcNAc and α-2,6 linked sialic acid residues. The other part of an antibody, called the Fab<unk> , contains variable sections that define the specific target that the antibody can bind. By contrast, the Fc<unk>  of all antibodies in a class are the same for each species; they are constant rather than variable. The Fc<unk>  is, therefore, sometimes incorrectly termed the<unk>  constant<unk> ". Fc binds to various cell receptors and complement proteins. In this way, it mediates different physiological effects of antibodies (detection of opsonized particles; cell lysis; degranulation of mast cells, basophils, and eosinophils; and other processes).
Fragment crystallizable region
Neutralizing domain
Common gamma chain
N-terminal telopeptide
Neoepitope
C-terminal telopeptide
Therapeutic interfering particle
Decay-accelerating factor