Polymeric immunoglobulin receptor

Polymeric immunoglobulin receptor (pIgR) is a type of protein that plays a crucial role in the immune system. It is responsible for the transportation of immunoglobulins from the bloodstream to the mucosal surfaces of the body, providing a first line of defense against invading pathogens.

Structure

The polymeric immunoglobulin receptor is a transmembrane protein that is composed of five domains: a transmembrane domain, a cytoplasmic domain, and three extracellular domains. The extracellular domains are responsible for binding to the immunoglobulin molecules, while the transmembrane and cytoplasmic domains are involved in the transportation process.

Function

The primary function of the pIgR is to transport immunoglobulin A (IgA) and immunoglobulin M (IgM) from the bloodstream to the mucosal surfaces of the body. This process, known as transcytosis, involves the receptor binding to the immunoglobulin molecules in the bloodstream, internalizing them into the cell, and then releasing them at the mucosal surface.

The pIgR also plays a role in the immune response by helping to neutralize pathogens at the mucosal surface. This is achieved by the IgA and IgM molecules binding to the pathogens and preventing them from invading the body's cells.

Clinical significance

Mutations in the pIgR gene can lead to a condition known as selective IgA deficiency, which is characterized by low levels of IgA in the mucosal surfaces. This can result in an increased susceptibility to infections, particularly of the respiratory and gastrointestinal tracts.

In addition, studies have suggested that the pIgR may play a role in the development of certain types of cancer, including breast cancer and colorectal cancer. However, further research is needed to fully understand this relationship.

See also

• Immunoglobulin A
• Immunoglobulin M
• Transcytosis
• Selective IgA deficiency