What is J chain and its function?

The joining (J) chain is a small polypeptide, expressed by mucosal and glandular plasma cells, which regulates polymer formation of immunoglobulin (Ig)A and IgM. J-chain incorporation into polymeric IgA (pIgA, mainly dimers) and pentameric IgM endows these antibodies with several salient features.

Do all antibodies have J chain?

A J chain is a protein component of the antibodies IgM and IgA. It is a 137 residue polypeptide, encoded by the IGJ gene….J chain.

JCHAIN
Species	Human	Mouse
Entrez	3512	16069
Ensembl	ENSG00000132465	ENSMUSG00000067149
UniProt	P01591	P01592

What antibodies have J chain?

The J chain is a part of the polymeric immunoglobulin molecules IgM and IgA. It is generally assumed that the J chain participates somehow in the polymerization of these molecules (Koshland, 1985). If B lymphocytes express high levels of J chain, the secreted IgM molecules are mostly pentamers.

How many J chains are there in IgM?

Although it is generally believed that pentameric IgM and dimeric IgA contain one J chain per polymeric molecule, Brandtzaeg (20) have reported two J chains for IgA and three or four J chains for IgM.

What are J chains and secretory pieces?

These polypeptides are called the secretory component (SC) and the J chain. While the SC, a large glycoprotein secreted by the lining epithelium of exocrine glands, is the primary distinguishing feature between serum and secretory IgA, the J chain is a small acidic polypeptide that is secreted by the immunocyte itself.

Why is J chain important?

The J chain is critical in the structure of SIgA because it is required for efficient polymerization of IgA and for the affinity of such polymers to the secretory component (SC)/polymeric (p)IgR.

Where is J chain found?

Amino acid sequences of purified J chain have been determined in the rabbit (Hughes, 1990). The chromosomal location of the J chain gene has been determined for mouse and human; in mouse it resides on chromosome 5 (Yagi et al., 1982) and in human, on the long arm of chromosome 4 (Max et al., 1986).

What is the role of secretory piece?

One identified function of secretory components is to protect IgA antibodies from degradation by the gastric acids and enzymes of the digestive system. This property is especially important in the transfer of immune system components during breastfeeding.

What is secretory IgG?

Secretory immunoglobulin A (IgA) is the predominant immunoglobulin isotype present in mucosal surfaces. Secretory IgA is composed of two IgA molecules (dimeric IgA), a joining protein (J chain), and a secretory component (SC). The dimeric IgA-J chain complex is produced by B lymphocytes in the submucosal tissues.

Where is IgA secreted?

IgA subclasses differ in distribution and function. IgA1 is present mainly in the serum (it accounts for 85 per cent of serum IgA) and predominates in secretion in the upper intestine and in the various mucosal glands. IgA2 predominates in secretion in the large intestine and in the female genital tract.

What is secretory antibody?

Secretory antibodies mediate removal of antigens from the mucosal lamina propria, in which antigens are bound to dimeric IgA and are subsequently transported to the luminal surface of the epithelial cells following endocytosis of the antigen–dimeric IgA–J chain–pIgR complex and its release into the mucosal lumen.

What is IgG and IgM positive?

Both SARS-CoV-2 IgM and IgG antibodies may be detected around the same time after infection. However, while IgM is most useful for determining recent infection, it usually becomes undetectable weeks to months following infection; in contrast, IgG is usually detectable for longer periods.

What is the meaning of IgM negative and IgG positive?

IgM negative, IgG positive There is recovery from the disease and the patient is not infectious. There may be some immunity to Covid-19, although it is not known yet to what extent and how long that immunity may last. Precautions should still be taken.

What does IgG positive mean Covid?

IgG antibodies remain in the blood after an infection has passed. These antibodies indicate that you may have had COVID-19 in the recent past and have developed antibodies that may protect you from future infection. It is unknown at this point how much protection antibodies might provide against reinfection.

What is the difference between IgA and IgG?

Immunoglobulin A (IgA): It’s found in the linings of the respiratory tract and digestive system, as well as in saliva (spit), tears, and breast milk. Immunoglobulin G (IgG): This is the most common antibody. It’s in blood and other body fluids, and protects against bacterial and viral infections.

What does IgM and IgG positive mean?

What does it mean if the specimen tests positive for IgM and/or IgG antibodies against virus that causes COVID-19? A positive test result with the qSARS-CoV-2 IgG/IgM Rapid Test indicates that antibodies to SARS-CoV-2 were detected, and the patient has potentially been exposed to COVID-19.