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Immunoglobulin light chain

 

 
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Immunoglobulin light chain
 
 
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] A light chain is the small polypeptide subunit of an antibody
Antibody

Antibodies are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacterium and viruses....
 (or immunoglobulin). A typical antibody is composed of two immunoglobulin (Ig) heavy chain
Heavy chain

The immunoglobulin heavy chain is the large polypeptide subunit of an antibody.A typical antibody is composed of two immunoglobulin heavy chains and two Ig light chains....
s and two Ig light chains.

e are two types of light chain in mammals,

Antibodies are produced by B lymphocytes which each express only one class of light chain. Once set, light chain class remains fixed for the life of the B lymphocyte.






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] A light chain is the small polypeptide subunit of an antibody
Antibody

Antibodies are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacterium and viruses....
 (or immunoglobulin). A typical antibody is composed of two immunoglobulin (Ig) heavy chain
Heavy chain

The immunoglobulin heavy chain is the large polypeptide subunit of an antibody.A typical antibody is composed of two immunoglobulin heavy chains and two Ig light chains....
s and two Ig light chains.

In humans

There are two types of light chain in mammals,
  • lambda chain (1, 2, 3, and 4)
  • kappa chain (only one type)


Antibodies are produced by B lymphocytes which each express only one class of light chain. Once set, light chain class remains fixed for the life of the B lymphocyte. In a healthy individual, the total kappa to lambda ratio is roughly 65 to 35, with a highly divergent ratio indicative of neoplasm.

In other animals

The immunoglobulin light chain genes in tetrapods can be classified into three distinct groups: kappa, lambda, and sigma (s). The divergence of the ?, ?, and s isotypes preceded the radiation of tetrapods. The s isotype was lost after the evolution of the amphibian lineage and before the emergence of the reptilian lineage.

Other types of light chains can be found in lower vertebrate
Vertebrate

Vertebrates are members of the subphylum Vertebrata, chordates with Vertebras or Vertebral columns. The grouping sometimes includes the hagfish, which have no vertebrae, but are genetically quite closely related to lampreys, which do have vertebrae....
s, such as the Ig-Light-Iota chain of Chondrichthyes
Chondrichthyes

Chondrichthyes or cartilaginous fishes are jawed fish with paired Fins, paired nares, scales, two-chambered hearts, and skeletons made of cartilage rather than bone....
 and Teleostei
Teleostei

Teleostei is one of three infraclasses in class Actinopterygii, the ray-finned fishes. This diverse group, which arose in the Triassic period, includes 20,000 extant species in about 40 orders; most living fishes are members of this group....
.

Camelid
Camelid

Camelids are members of the biological family Camelidae, the only living family in the suborder Tylopoda. Camels, dromedary, llamas, alpacas, vicu?as, and guanacos are in this group....
s are unique among mammals as they have fully functional antibodies which have two heavy chains, but lack the light chains usually paired with each heavy chain. The functional role of this separate repertoire is unknown as yet.

Structure

Only one type of light chain is present in a typical antibody, thus the two light chains of an individual antibody are identical.

Each light chain is composed of two tandem immunoglobulin domains
Immunoglobulin fold

An immunoglobulin fold is a common all-? protein fold that consists of a 2-layer sandwich of ~7 antiparallel beta sheet arranged in two beta sheet....
:
  • one constant (IgC) domain
  • one variable domain (IgV) that is important for binding antigen
    Antigen

    An antigen is a substance that prompts the generation of antibodies and can cause an immune response. The word originated from the notion that they can stimulate antibody generation....


The approximate length of a light chain protein is from 211 to 217 amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
s.

In pathology

Ig light chains produced in neoplastic plasma cells, e.g. in multiple myeloma
Multiple myeloma

Multiple myeloma is a cancer of plasma cells. These immune system cells are formed in bone marrow, are numerous in lymphatics and produce antibody....
, are called Bence Jones protein
Bence Jones protein

A Bence Jones protein is a monoclonal globulin protein found in the blood or urine, with a molecular weight of 20 Atomic mass unit. Finding this protein in the context of end-organ manifestations such as malignant bone marrow cancer, renal failure, lytic bone disease, or anemia, or large numbers of plasma cells in the bone marrow of patients...
s.

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