Which fragment of an antibody contains the Fc region?

• A. Fab fragment
• B. Fc fragment
• C. Heavy chain
• D. Hinge region

Answer: (B)

The Fc region is the tail portion of an antibody formed by the constant domains of the heavy chains. It is the part responsible for triggering effector functions, such as binding to Fc receptors on immune cells and activating complement, rather than binding the antigen itself. This region can be separated from the antigen-binding portions by proteolytic digestion (for example, with papain), which yields two Fab fragments that bind antigen and one Fc fragment that mediates effector activity. The hinge region is the flexible linker between the Fab and Fc portions within the heavy chain, not the Fc piece itself.