Antibody fragment

Overview

An antibody fragment is a portion of an antibody that retains the ability to bind to an antigen. Antibodies, also known as immunoglobulins, are large, Y-shaped proteins produced by B cells that are used by the immune system to identify and neutralize foreign objects such as bacteria and viruses.

Structure of Antibodies

Antibodies are composed of two identical heavy chains and two identical light chains, forming a Y-shaped structure. The tips of the "Y" contain the variable regions, which are responsible for antigen binding. The stem of the "Y" is known as the Fc region, which interacts with cell surface receptors and the complement system.

Diagram of an antibody showing the Fab and Fc regions.

Types of Antibody Fragments

Antibody fragments can be generated through enzymatic digestion or recombinant DNA technology. The main types of antibody fragments include:

Fab Fragments

Fab (Fragment antigen-binding) fragments are produced by the enzymatic digestion of antibodies with papain. Each Fab fragment contains one complete light chain and part of a heavy chain, including the variable region, allowing it to bind to antigens.

F(ab')2 Fragments

F(ab')2 fragments are produced by the enzymatic digestion of antibodies with pepsin. This results in a fragment that contains two antigen-binding Fab portions linked together, providing bivalent binding to antigens.

Fc Fragments

The Fc (Fragment crystallizable) region is the tail part of an antibody that interacts with cell surface receptors and the complement system. It is responsible for the effector functions of antibodies, such as antibody-dependent cellular cytotoxicity (ADCC) and complement activation.

Applications of Antibody Fragments

Antibody fragments have several applications in research, diagnostics, and therapy due to their smaller size and ability to penetrate tissues more effectively than full-length antibodies.

Therapeutic Use

Antibody fragments are used in the development of biopharmaceuticals for the treatment of diseases such as cancer, autoimmune disorders, and infectious diseases. Their smaller size allows for better tissue penetration and reduced immunogenicity.

Diagnostic Use

In diagnostics, antibody fragments are used in immunoassays and imaging techniques to detect the presence of specific antigens. Their ability to bind specifically to target molecules makes them valuable tools in clinical diagnostics.

Related Pages

• Antibody
• Immunoglobulin
• Antigen
• B cell
• Immune system