Association of Human Milk SIgA Antibodies with Maternal Intestinal Exposure to Microbial Antigens

Abstract

Human colostrum S-IgA and mature breast milk contain large quantities of secretory IgA (S-IgA)^1–3. In general, the concentration of milk SIgA is higher in the early postpartum period; than in the later stages of lactation^3–5. The content of S-IgA is the result of the additive presence of a great variety of specific S-IgA antibodies that are formed locally in the mammary gland by lymphocytes that had been primed at the intestinal level by microbial and food antigens, and that migrated to the mammary gland under the influence of hormones^6–8. In such a way, antibodies directed against Shigella,Salmonella and Escherichia coli somatic antigens, Vibrio cholera and E. coli toxins, rota- and polioviruses, and cow milk, black beans and soy beans proteins, have been detected in human colostrum and milk samples obtained in different ecosystems^1,9–14. The ingestion of human milk containing high levels of specific antibodies has been shown to be associated with protection against diarrheal illnesses^15,16 and food allergies¹⁷ in the breast-fed infants. Nevertheless, prospective studies have demonstrated that the presence and levels of specific S-IgA antibodies in milk do not remain constant during lactation^18,19, suggesting that its protective capacity also varies over time.