Caries Process, Prevention and Management: The Host
Course Number: 712
Course Contents
Secretory Immunoglobulin A (IgA)
This is the dominant immunoglobulin in the healthy mouth.1 SigA is produced by gland-associated immunocytes that are scattered in acini and in clusters adjacent to salivary ducts. SigA is composed of two molecules of heavy and light chains, a secretory component that protects the immunoglobulin from being degraded by proteolytic enzymes, and a J chain. This is a unique joining chain not found in any other immunoglobin that connects the two IgA molecules into a dimeric structure.16
Figure 10. Secretory Immunoglobulin A (IgA)
SigA can agglutinate oral bacteria, such as S. mutans, modulate enzyme activity, and inhibit the adherence of bacteria to the buccal epithelium and to enamel.17-19 It does well at interfering with the initial colonization of caries-associated microflora on the tooth surface, but being a salivary protein, it does not always have access to bacteria that are deeper in periodontal pockets. SigA is also a poor activator of the complement system, the biochemical cascade that helps antibodies physically clear pathogens. It is also a poor opsonizer that does not reliably make bacterial cells susceptible to phagocytosis. A recent study identified sIgA as a potential biomarker for early childhood caries, demonstrating high sensitivity and specificity.20