Native Human IgA protein

Supplementary information

This supplementary information is collated from multiple sources and compiled automatically.

Immunoglobulin A (IgA) also known as sIgA in its secretory form is an important component of the immune system. With a molecular weight of approximately 160 kDa IgA exists as a monomeric or dimeric structure. It is primarily expressed in mucosal areas such as the respiratory tract gastrointestinal tract and urogenital tract while also being present in secretions like saliva tears and breast milk. In its dimeric form IgA associates with a joining (J) chain and a secretory component which facilitates its transport across mucosal barriers.

Biological function summary

IgA functions as a first line of defense in immune responses occurring at mucosal surfaces. Its primary role is to neutralize pathogens toxins and prevent their attachment and penetration through epithelial cells. This antibody does not form part of a larger complex but plays an important role in immune exclusion by trapping antigens in the mucus layer. Additionally IgA can mediate antibody-dependent cellular cytotoxicity and engage with specific receptors like FcαRI (CD89) on immune cells further enhancing its protective capabilities.

Pathways

IgA participates in the mucosal immune response which is a sub-component of the broader immune system pathways. It is closely associated with the polymeric immunoglobulin receptor (pIgR) which transports IgA to the mucosal surfaces. The pathway involves recombination activation proteins (RAG) during its class-switching process in B cells differentiating from IgM-producing cells to those secreting IgA. These pathways are integral to maintaining the mucosal environment and protecting against pathogens.

Alterations or deficiencies in IgA can lead to increased susceptibility to infections and disorders like IgA nephropathy and celiac disease. In IgA nephropathy IgA deposits in the kidneys result in inflammation and damage to renal tissues. Celiac disease involves an immune reaction to gluten where IgA antibodies against tissue transglutaminase (tTG) contribute to intestinal damage. Both conditions illustrate the importance of IgA in maintaining immune balance and its connection with disease pathologies.