Antibody Overview | Phage Display Overview | Utility of Selected Antibodies | Glossary

Antibodies are proteins naturally produced by the body's immune system in response of invasion by foreign antigens such as bacteria or viruses. Antibodies produced by the humoral immune system are so diverse that they are essentially able to bind target molecules of any nature whether they are proteins, nucleic acids, carbohydrates, or lipids. While diverse, each individual antibody produced maintains high specificity and affinity to its antigen. Such binding helps the elimination of the foreign antigens, including tumor cells from a human body. Based on their unique properties, antibodies have been widely used as powerful tools in diagnostic and therapeutic applications as well as in basic biomedical research.

All antibodies (also known as immunoglobulins; Ig) share the same basic structure consisting a 'heavy' chain and a 'light' chain. The binding specificity of the antibody to a given antigen is provided by the highly variable nature of the antigen binding region (V_H+V_L). Utilizing recombinant DNA technology, functional antibodies can be expressed not only as full-length intact forms but can also be expressed as antigen binding domains such as Fab fragments, consisting of the entire light chain and partial heavy chain, as single-chain variable region fragments (sFv), consisting only the heavy and light variable regions linked by a short interchain linker of usually 15 amino acids or even as domain antibodies consisting of only the heavy chain variable region.

Traditionally, immunization of rodents has been used as the source of B cells (immunoblasts) to produce monoclonal antibodies. This technique has a long history of providing useful research reagents to investigators. However, use of research animals for this purpose is time consuming and becomes more restrictive. In addition, clinical use of these rodent monoclonal antibodies has resulted in human anti-mouse antibody responses (HAMA), which has greatly limited their therapeutic potential. Recently alternative methods including phage display have been developed that now allow investigators to bypass in vivo immunizations of animals or humans to produce human antibodies that can be used as research reagents and for therapeutic purposes.