IMMUNOGLOBULIN-A SUPPLEMENTATION ABROGATES BACTERIAL TRANSLOCATION AND PRESERVES THE ARCHITECTURE OF THE INTESTINAL EPITHELIUM

Background. Breast milk has been shown to prevent gut-origin infection s in neonates through undefined mechanisms. Putative protective factor s in breast milk include immunoglobulin (Ig)A, IgG, and lactoferrin. W e examined their role in bacterial translocation in neonatal rabbits. Methods. IgA, IgG, and lactoferrin were isolated from rabbit breast mi lk through gelfiltration and ion-exchange chromatography. Neonates wer e randomized to receive breast milk, formula alone, or formula supplem ented with IgA, IgG, or lactoferrin. Quantitative cultures were perfor med on day 7 for bacterial translocation. Hematoxylin-eosin-stained se ctions of distal ileum were examined by light microscopy. Transmucosal bacterial passage was determined in vitro, and the ileal mucosal memb ranes were examined by confocal microscopy. Results. IgA supplementati on abrogated bacterial translocation. IgG and lactoferrin had no signi ficant effect. Neonates that received IgA or breast milk gained more w eight than those in the other groups. IgA reduced transmucosal bacteri al passage in vitro. In contrast to the normal-appearing distal ileum of neonates fed breast milk, intestinal epithelium from neonates that received formula or formula with IgG or IgA demonstrated prominent vac uoles by light microscopy. Those fed formula alone or formula with lac toferrin had slightly shortened villi. Conclusions. IgA supplementatio n prevents bacterial translocation by enhancing gut mucosal barrier fu nction.