Fragment crystallizable region of immunoglobulins (Fc region)

The **fragment crystallizable region (Fc region)** of immunoglobulins is the constant tail portion of an antibody molecule, composed of the constant domains of the heavy chains (excluding the antigen-binding variable domains). The Fc region is responsible for interacting with cellular Fc receptors (such as Fc gamma, Fc epsilon, or Fc alpha receptors) and proteins of the complement system, allowing antibodies to activate key immune mechanisms such as phagocytosis, cell lysis, mast cell degranulation, and antibody-dependent cellular cytotoxicity[1][3][4][5][6][9]. There are different Fc regions depending on the antibody isotype (IgG, IgA, IgM, IgD, IgE), with varying domain compositions and effector functions. Glycosylation of the Fc region is critical for its interaction with Fc receptors and complement proteins and directly impacts therapeutic efficacy and immunogenicity[1]. The Fc region serves as the primary interface for antibody-based therapies to recruit immune effector functions, making it a central target in the design and engineering of therapeutic antibodies and antibody fragments.

Other names

Fc fragmentFc domainFragment crystallizable regionConstant region (incorrect/less accurate)Immunoglobulin Fc

Engages Fc gamma, Fc epsilon, and other Fc receptors on immune cells to initiate immune cell recruitment and activation. Activates complement-dependent cytotoxicity (CDC). Triggers antibody-dependent cellular cytotoxicity (ADCC). Mediates antibody-dependent cellular phagocytosis (ADCP).