Immunoglobulin A (salivary) (IgA (salivary) or sIgA)

Immunoglobulin A (salivary), also known as secretory IgA (sIgA), is the predominant antibody isotype in mucosal secretions such as saliva, tears, colostrum, and gastrointestinal fluids. It is produced by plasma cells in a dimeric or polymeric form and transported across epithelial cells into secretions via the polymeric immunoglobulin receptor (pIgR); the extracellular portion of this receptor (secretory component) is covalently linked to the IgA, protecting it from enzymatic degradation[1][5]. In saliva and other secretions, sIgA forms the body's first line of defense at mucosal surfaces by neutralizing pathogens, preventing their adherence to and invasion of epithelial cells, a process known as immune exclusion[4][5]. sIgA also participates in intracellular neutralization of viruses and can help excrete antigens from the lamina propria to the lumen[4]. IgA has two subclasses: IgA1 and IgA2; both are found in secretions, but IgA2 is more resistant to bacterial proteases and is thus more prevalent in some secretions[3][5]. Salivary IgA is considered a biomarker of mucosal immune function and stress but is itself not a direct therapeutic target such as a receptor, enzyme, or transporter[5]. Salivary immunoglobulin A (sIgA) is the main antibody of mucosal immunity in saliva, functioning as a frontline defense against pathogens at moist body surfaces[5][4]. It is essential for immune exclusion at mucosal sites but is not a canonical therapeutic target, receptor, or enzyme. It serves as an important biomarker of mucosal immune status and response to stress[5].

Other names

Secretory immunoglobulin AsIgAsalivary IgA