Immunoglobulin fragment crystallizable region (Fc region)

The immunoglobulin fragment crystallizable region, commonly known as the Fc region, is the constant tail portion of an antibody molecule that interacts with cell surface Fc receptors and complement proteins. The Fc region is composed of constant domains of the antibody heavy chains (excluding the first domain) and mediates effector functions after antigen binding, such as the activation of complement pathways, binding to immune cell receptors, and modulation of adaptive and innate immune responses[1][2][3][4][5][6][7][8]. Different antibody classes (IgG, IgA, IgM, IgD, and IgE) feature unique Fc regions that determine their isotype-specific effector functions. Fc-mediated processes include antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), complement-dependent cytotoxicity (CDC), and the degranulation of mast cells and basophils. The Fc region is a critical determinant of antibody therapeutic efficacy, and its structure and glycosylation status can be engineered to enhance or silence particular immune effector functions[1][2][7]. Numerous therapeutic monoclonal antibodies and Fc fusion proteins use the Fc region as a platform for engaging the immune system against cancer cells, infectious diseases, and inflammatory processes.

Other names

Fc regionFragment crystallizable regionFc fragment

Antibody-dependent cellular cytotoxicity (ADCC) via Fc receptor binding; Antibody-dependent cellular phagocytosis (ADCP) via Fc receptor binding; Complement-dependent cytotoxicity (CDC) via complement binding; Modulation of immune responses (e.g., through agonism or antagonism of Fc receptors)