330
Antibody Molecules, Genetic Engineering of
Keywords
Antibody/Antigen
Antibodies are proteins known as
immunoglobulins
(Igs), which are produced by the
immune system in response to the presence of a foreign substance. Antigens are
molecules (usually proteins) on the surface of cells, viruses, fungi, bacteria, and some
nonliving substances such as toxins, chemicals, drugs, and foreign particles, which are
recognized and speciFcally bound by antibodies. The immune system recognizes
immunogenic antigens (also known as
immunogens
), and produces antibodies that
destroy or neutralize substances or organisms containing antigens.
Antibody-dependent Cellular Cytotoxicity (ADCC)
Cell-killing reaction in which the ±c receptor bearing killer cells recognizes target cells
via speciFc antibodies.
Bacteriophage
Bacteriophages or phages are viruses that infect bacteria. Bacteriophage
λ
is a
temperate phage, which can grow lytically lysing the bacteria and forming a clear
plaque on a lawn of bacteria. Infection with Flamentous phages such as M13 is not
lethal and the host bacteria do not lyse. Instead, their rate of growth slows and they
form turbid plaques on the bacterial lawn.
Complement
Group of serum proteins participating in the lysis of foreign cells and pathogens [a
process known as
complement-dependent cytotoxicity
(CDC)]; they also play an important
role in phagocytosis.
Constant Region
Portion of the antibody molecule exhibiting little variation and determining the isotype
(class or subclass) of the antibody.
Fab
The ±ab fragment is a monovalent antigen-binding fragment of an antibody that
consists of one light chain and part of one heavy chain (the variable region and the Frst
constant region domain). It can be obtained by digestion of intact antibody with papain
or by genetic engineering techniques.
Fc
The ±c is a nonantigen binding fragment of an antibody that consists of the
carboxy-terminal portion of both heavy chains. It can be obtained by papain digestion of
an intact antibody. Two ±abs and one ±c fragment comprise a complete IgG antibody.
Fv/scFv
The ±v is a monovalent antigen-binding fragment of an antibody composed of the
variable regions from the heavy and light chains. sc±v fragments are composed of the
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