Mucosal IgA has generally been viewed as an immune barrier to prevent
the adherence and absorption of antigens. Recent studies employing pol
arized epithelial monolayers have suggested two additional functions f
or mucosal IgA. One is to neutralize intracellular microbial pathogens
, such as viruses, directly within epithelial cells. The second is to
bind antigens in the mucosal lamina propria and excrete them through t
he adjacent epithelium into the lumen, thereby ridding the body of loc
ally formed immune complexes and decreasing their access to the system
ic circulation.