Fab-Independent Antiadhesion Effects of Secretory Immunoglobulin A on S-Fimbriated Escherichia coli Are Mediated by Sialyloligosaccharides

S-fimbriated Escherichia coli strains cause sepsis and meningitis in newborns and are known to recognize the carbohydrate sequence sialyl-(α2-3)-galactoside. We show that adhesion of cloned S-fimbriated E. coli to human epithelial cells is inhibited Fab independently by sialyloligosaccharides on secretory immunoglobulin A (s-IgA). This indicates an anti-infective function of s-IgA (Fc), particularly in early human milk.