IgA and antigen sampling

Abstract

As the primary immunoglobulin class in mucosal secretions, secretory immunoglobulin A (SIgA) antibodies function as the immunological frontline, protecting the vulnerable surfaces of the intestinal epithelium from pathogenic bacteria, viruses, and toxins encountered in the normal human diet. SIgA also serves as a barrier to commensal microbiota (Johansen et al., 1999; Kelly et al., 2005; Macpherson et al., 2000;), some of which are opportunistic pathogens capable of causing disease if afforded access to the systemic compartment. Protection is achieved primarily by immune exclusion, a general term referring to the ability of SIgA to coat intestinal antigens, thereby (1) preventing their attachment to epithelial cell receptors and (2) promoting their clearance from the intestinal lumen via peristalsis (Lamm, 1997). SIgA is also of critical importance to neonates whose mucosal immune systems are in the early stages of development. In humans, SIgA is the major immunoglobulin class in colostrum and breast milk, providing passive immunity to a variety of enteric pathogens (Brandtzaeg, 2003).