Each Mother Passes on a Unique Pool of Antibodies From Breast Milk to Her Baby

Everyone’s breast milk contains a unique collection of antibodies that are remarkably stable throughout breastfeeding and across pregnancies, according to a University of Pittsburgh School of Medicine study in the Journal of Experimental Medicin. Because a baby’s early immunity is controlled by antibodies from breast milk, the new research sheds light on why protection against different infections varies among infants, and why some develop a life-threatening intestinal disease called necrotizing enterocolitis (NEC).

Necrotizing Enterocolitis And the Dangers

While the antibody profiles of the individual milk donors in the study differed greatly, the researchers found that antibodies from the same donor were quite similar over time – even months. This means that a baby’s parents who lack certain antibodies – such as those that fight off NEC – will never get that immunity. This could explain why some babies develop NEC and others do not. According to researchers, NEC is a devastating inflammatory bowel disease that primarily affects premature babies. With NEC, inflammation occurs and the damaged intestinal tissue often has to be surgically removed.

The resulting short intestine is not always sufficient to ensure survival. The damaged intestinal tissue can also allow bacteria that are normally trapped in the intestinal cavity to enter the abdominal cavity and cause an infection. This process can be extremely critical for a baby and may even be fatal. As the exact causes of NEC are unclear, there is currently no specific treatment and prevention remains a challenge. NEC, which is associated with a family of bacteria called Enterobacteriaceae, has been found to be about two to four times more common in formula-fed infants than in breast-fed infants.

How infants Acquire Immunity

Before their immune system is fully developed, infants are protected from harmful bacteria by antibodies that are transferred via the mother’s placenta and breast milk. These antibodies bind to the bacteria in the gut and prevent them from invading the host. In an earlier study, lead study author Tmothy Hand, Ph.D., and his team found that Enterobacteriaceae in stool samples from healthy infants were largely bound by maternal antibodies. In contrast, infants who later developed NEC had more bacteria that escaped binding. Hand suspected that the different immunity of infants to NEC was due to different mothers passing on different antibodies, and the new study supports this idea.

The researchers analyzed donor milk from the Human Milk Science Institute and Biobank in Pittsburgh and the Mommy’s Milk Human Milk Research Biorepository in San Diego. Using an area of ​​different bacteria, they measured which strains the antibodies of each donor were bound to. The antibody profiles of each donor looked completely different. During pregnancy, B cells migrate from the intestines to the mammary gland, where they begin to produce antibodies. The mother tries to protect her child with antibodies that she uses to protect her intestines. Different women have lived different lives, have different microbiomes, and faced different infections, so it makes sense that the antibodies in breast milk reflect this variability.

During breastfeeding, breast milk changes from highly concentrated, protein-rich colostrum to mature milk. To find out whether the composition of the antibodies also changes, Hand and his team compared breast milk from the same donors over time. They also examined the same donors across multiple pregnancies. Not only were the antibodies similar across donors across pregnancy, they were also remarkably stable between infants. This suggests that once B cells arrive in breast tissue, they do not leave. This is important for understanding how infants acquire immunity and how they deal with infections. The researchers also wondered whether the antibodies in breast milk differ if a donor gave birth prematurely. That wasn’t the case. Women who give birth prematurely have the same number of antibodies and the same diversity as those who give birth at a normal time.

Breast Milk as Protection Against Diseases

Other studies suggest that one’s own breast milk is the best food for reducing the likelihood of developing NEC in premature babies, but when this is not available, donor milk is an important substitute or supplement. This milk is sterilized to kill bacteria, but whether this process also affects antibodies had not been studied before. Hand and his team found that pasteurization lowers antibody levels in donor milk. Although this likely means that infants fed donor milk receive fewer antibodies than those who receive milk directly from their mother, Hand said more research is needed to understand what levels of antibodies protect against diseases like NEC . In the future, a better understanding of the specific bacteria that are most dangerous to premature babies at risk of NEC could help researchers develop antibodies that could be added to infant formula or breast milk to boost immunity.

Breastfeeding