GLOSSARY

Immunoglobulin A is an antibody class that contributes to defence at mucosal surfaces. In blood it is mainly present as a single immunoglobulin unit. Secretory IgA at many mucosal surfaces commonly consists of two joined units associated with a secretory component that helps protect it in the local environment.

At a mucosal surface

• Production: Plasma cells in tissue under the epithelium produce polymeric IgA.
• Transport: An epithelial receptor carries the antibody across the cell. A portion of that receptor remains associated with secretory IgA.
• Action: IgA can bind particles and microbes and reduce their attachment to epithelial cells without requiring a strong local inflammatory response.

Saliva as a sample