What is the primary function of secretory IgA (sIgA) found in saliva?

Secretory IgA (sIgA) is the predominant immunoglobulin in saliva and serves as the first line of immunological defense in the oral cavity. Its primary function is antimicrobial: it prevents microbial adhesion to mucosal surfaces (immune exclusion), neutralizes bacterial toxins and viruses, and inhibits bacterial colonization. sIgA is produced by plasma cells in salivary glands and is stabilized by a secretory component that protects it from proteolytic degradation in the oral environment. It is broader than simply 'antibacterial' as it also acts against viruses and fungi.