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Value Of Transplacental Versus Breast Milk Antibodies: Babies acquire maternal antibodies in utero and through breast milk. Breast milk antibody absorption is a minor, not major, source of circulating antibodies in the newborn (1). Major source of circulating IgG antibodies in newborns are maternal antibodies in the form of IgG transported in utero through the placenta and absorbed by fetal enterocytes (gut epithelial cells) via FcRn receptors (Neonatal Fc receptor) that specialize in antibody absorption  (2). OTOH, representing mother’s mucosal immune history to food antigens and microbes, breast milk secretory antibodies (sIgA > sIgM >sIgG) are very much useful at the baby’s mucosal surfaces, helping them as they get colonized with microbes (see figure below from 3).

How Breast Milk Antibodies Are Transported Across Baby’s GI Tract: Two features different between newborns and older age make it easier for breast milk antibodies to 1st, pass intact through the stomach, and 2nd, get absorbed in the intestine.

  • Newborn stomach has a more immature digestive function. The 1st week of life it is actually relatively achlorhydric (low production of stomach hydrochloric acid), and stomach pH lowers slowly towards adult levels over the 1st two years of life (4). Since newborn stomach has less acidic pH, greater proportion of molecules including proteins such as antibodies or sugars and other nutrients in breast milk can pass through intact from the stomach.
  • Newborn intestine has greater intestinal permeability that allows a greater proportion of breast milk antibodies to pass through (1, 5, 6). Oral nutrition jumpstarts the process of decreasing newborn intestinal permeability, ‘gut closure‘ (7), and some studies suggest breast milk helps speed up this process (8, 9).

Both direct and indirect evidence show breast milk antibodies pass through into the newborn.

Direct evidence

  • Experiments show specific antibodies from human colostrum and breast milk show up in newborn blood circulation (10, 11).
  • Other experiments also show newborn infant’s GI tract remains permeable to sugars and proteins (5, 6, 7, 8).

Indirect evidence comparing disease susceptibility between exclusively breastfed versus non-breastfed infants in field studies showed

  • Non-breastfed infants are 25X more likely to die from diarrheal diseases compared to those exclusively breastfed (11).
  • Breast-feeding protects against several respiratory tract, ear and urinary tract infections, botulism, necrotizing enterocolitis (11).
  • Breast-feeding’s so effective in protecting newborns against infectious diseases that the WHO estimates a 40% worldwide increase in breastfeeding could reduce diarrheal deaths by 66% and respiratory infection deaths by 50% in children <18 months of age (12).

Finally, though stomach breaks down proteins, process isn’t 100% even in adults, and small amounts of antigenically intact proteins pass through. Antigenically means sufficiently intact so antibody-making B cells can bind and respond. This is why even healthy individuals have circulating antibodies to food proteins (13, 14) such as antibodies that pass from mother to baby, and why skin prick tests work for diagnosing food allergies.

Bibliography

1. Weaver, L. T., et al. “The ontogeny of serum IgA in the newborn.” Pediatric Allergy and Immunology 2.2 (1991): 72-75.

2. Israel, E. J., et al. “Immunoglobulin G binding sites on the human foetal intestine: a possible mechanism for the passive transfer of immunity from mother to infant.” Immunology 79.1 (1993): 77. http://www.ncbi.nlm.nih.gov/pmc/…

3. Brandtzaeg, Per. “Mucosal immunity: integration between mother and the breast-fed infant.” Vaccine 21.24 (2003): 3382-3388.

4. Chapter 5, Drug Therapy and Breastfeeding, Thomas W. Hale, Page 144. Breastfeeding and Human Lactation, 3rd Edition, Jan Riordan, 2005.

5. Weaver, L. T., M. F. Laker, and R. Nelson. “Intestinal permeability in the newborn.” Archives of disease in childhood 59.3 (1984): 236-241. http://adc.bmj.com/content/59/3/…

6. Van Elburg, R. M., et al. “Intestinal permeability in relation to birth weight and gestational and postnatal age.” Archives of Disease in Childhood-Fetal and Neonatal Edition 88.1 (2003): F52-F55. Intestinal permeability in relation to birth weight and gestational and postnatal age

7. Colome, Gemma, et al. “Intestinal permeability in different feedings in infancy.” Acta Paediatrica 96.1 (2007): 69-72.

8. Catassi, C., et al. “Intestinal Permeability. Changes during the First Month: Effect of Natural versus Artificial Feeding.” Journal of pediatric gastroenterology and nutrition 21.4 (1995): 383-386. Intestinal Permeability. Changes during the First Month: Eff… : Journal of Pediatric Gastroenterology and Nutrition

9. Goldman, Armond S. “Modulation of the gastrointestinal tract of infants by human milk. Interfaces and interactions. An evolutionary perspective.” The Journal of nutrition 130.2 (2000): 426S-431S. Modulation of the Gastrointestinal Tract of Infants by Human Milk. Interfaces and Interactions. An Evolutionary Perspective

10. Ogra, S. S., D. Weintraub, and Pearay L. Ogra. “Immunologic aspects of human colostrum and milk III. Fate and absorption of cellular and soluble components in the gastrointestinal tract of the newborn.” The Journal of Immunology 119.1 (1977): 245-248.

11. Hanson, Lars A. “Breastfeeding provides passive and likely long-lasting active immunity.” Annals of Allergy, Asthma & Immunology 81.6 (1998): 523-537.

12. World Health Organization (WHO). “Working group on breast feeding: science and society.” Pontif Acad Sci Doc 20 (1995): 1-33.

13. Paganelli, R. O. B. E. R. T. O., D. J. Atherton, and ROLAND J. Levinsky. “Differences between normal and milk allergic subjects in their immune responses after milk ingestion.” Archives of disease in childhood 58.3 (1983): 201-206. Differences between normal and milk allergic subjects in their immune responses after milk ingestion.

14. Husby, Steffen. “Normal immune responses to ingested foods.” Journal of pediatric gastroenterology and nutrition 30.1 (2000): S13-S19.

https://www.quora.com/How-do-antibodies-in-breast-milk-get-into-babies/answer/Tirumalai-Kamala

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