Fragment crystallizable region



The fragment crystallizable region (Fc region) is the tail region 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 region is composed of two identical protein fragments, derived from the second and third constant domains of the antibody's two heavy chains; IgM and IgE Fc regions contain three heavy chain constant domains (CH domains 2-4) in each polypeptide chain.

Function
Fc binds to various cell receptors and complement proteins.

In this way, it mediates different physiological effects of antibodies (opsonization, cell lysis, degranulation of mast cells, basophils and eosinophils and other processes).