Moms pass unique antibodies to their babies through their breast milk: study

By Alice Clifford via SWNS

Mothers pass unique antibodies to their babies through their breast milk - making some infants more protected than others, reveals a new study.

As a baby’s early immunity is directed by antibodies from breast milk, the new findings show why protection against different infections varies among infants.

It explains why some develop a life-threatening gut disease called necrotizing enterocolitis (NEC).

If a mom doesn’t have the specific antibodies that fend off NEC, their baby will never receive that immunity.

NEC is an inflammatory gut disease that mainly affects preterm infants, with around one in 40 babies admitted to neonatal units in the UK developing the disease.

While most babies are successfully treated, it can be fatal.

NEC has been linked with a family of bacteria called Enterobacteriaceae and is around two to four times more frequent in formula-fed babies than those fed breast milk.

Study author Dr. Timothy Hand, an associate professor of pediatrics and immunology at Pittsburgh School of Medicine, US, said: “While each milk donor in our study had very different antibody profiles from one another, we found that antibodies from the same donor were quite similar over time — even across the span of months.

“This means that if a baby’s parent happens to lack particular antibodies — such as those that fend off NEC, they’re never going to receive that immunity.

“This could help explain why some babies get NEC and others don’t.”

Before their immune system matures, babies are protected from harmful bacteria by antibodies transferred via the mother’s placenta and through breast milk.

These antibodies bind to bacteria in the intestine, preventing them from invading the host.

The team analyzed donor breast milk and by using an array of different bacteria they measured which strains each donor’s antibodies bound to.

Dr. Hand said: “Individual donors’ antibody profiles looked completely different, which is what we had expected but were able to show for the first time.

“During pregnancy, B cells travel from the intestine to the mammary gland, where they start making antibodies.

“The mum is trying to protect her infant using antibodies that she uses to protect her own intestine.

“Different women have led different lives, have different microbiomes and have encountered different infections, so it makes perfect sense that breast milk antibodies would reflect that variability.”

Throughout the breastfeeding period, a mother’s milk changes from highly concentrated protein-rich colostrum into mature milk.

To learn whether antibody composition changes too, the scientists compared breast milk from the same donors over time. They also looked at the same donors over multiple pregnancies.

Dr. Hand added: “Not only were antibodies similar in donors across one pregnancy, they were also remarkably stable between infants.

“This suggests that when B cells arrive in the breast tissue, they don’t leave.

“This is important for understanding how babies acquire immunity and how they deal with infections.”

The researchers also asked whether breast milk antibodies were different if a donor delivered prematurely.

Dr. Hand said: “Some B cells move to the mammary gland during the third trimester, so we wondered if a person delivers before this trimester is complete, would their milk have fewer antibodies?

“The good news was that we found no difference. Individuals who deliver preterm have just as many antibodies and the same diversity as those who deliver full-term.”

Other studies reveal that a mother’s own milk is the best food for reducing a premature baby’s likelihood of developing NEC, but if that isn’t available, donor milk is an important substitute or supplement.

Donor milk is sterilized and pasteurized, reducing antibody levels in the milk.

As a result, the infants given this milk receives fewer antibodies than those who are fed it directly from their mother.

In the future, a better understanding of specific bacteria that are most dangerous for preterm infants at risk of NEC could help researchers develop antibodies that could be added to formula or breast milk to boost immunity.

The study was published in the Journal of Experimental Medicine.