Mother transfers unique breast milk antibodies to the baby

Breast milk contains immunoglobulin A (IgA), which is essential for defending against enteric pathogens and influencing the infant’s intestinal flora.

According to a new study from the University of Pittsburgh School of Medicine, each person’s breast milk has a distinctive collection of antibodies that are unexpectedly constant throughout lactation and across pregnancies. The new study shows why newborns’ resistance to various illnesses differs and why some acquire the potentially fatal gut condition necrotizing enterocolitis (NEC). 

Senior author Timothy Hand, Ph.D., associate professor of pediatrics and immunology at Pitt’s School of Medicine and UPMC Children’s Hospital of Pittsburgh, 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, “If a baby’s parent lacks particular antibodies, such as those that fend off NEC, they will never receive that immunity. This could help explain why some babies get NEC, and others don’t.”

According to the study, antibodies from the same donor remained remarkably consistent over time, even over several months. This implies that a newborn won’t ever acquire immunity if one or both parents don’t have specific antibodies, such as those that protect against NEC. This may aid in illuminating why some infants get NEC while others do not.

Mostly affecting premature infants, NEC is a fatal inflammatory gastrointestinal condition. It is associated with the Enterobacteriaceae family of bacteria. It affects babies fed formula two to four times more frequently than breastfed babies. Babies are protected from hazardous microorganisms before their immune systems develop by antibodies passed through the placenta and breast milk from the mother. 

These antibodies stop intestinal bacteria from infecting the host by attaching to them. In a previous investigation, Hand and his group discovered maternal antibodies bound most Enterobacteriaceae in fecal samples from healthy babies.

In contrast, more bacteria avoided binding in infants who later developed NEC. The current study supports Hand’s hypothesis that variations in babies’ immunity to NEC were caused by various moms passing along different antibodies.

He said, “Individual donors’ antibody profiles looked completely different, which is what we had expected but were able to show for the first time. B cells travel from the intestine to the mammary gland during pregnancy, making antibodies. The mom is trying to protect her infant using antibodies to protect her 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.”

The Human Milk Science Institute and Biobank in Pittsburgh and Mommy’s Milk Human Milk Research Biorepository in San Diego provided the donor breast milk. Each donor’s antibodies were evaluated for their reactivity to different strains. The researchers discovered that each donor’s antibody profile appeared unique, which they had anticipated but could never demonstrate. 

The study also investigated whether preterm delivery affected the composition of breast milk antibodies. They hypothesized that if a woman delivers before the third trimester is finished, her milk would have less antibodies since some B cells migrate to the mammary gland at this time.

Other research indicates that mother’s milk is the best food to minimize a premature baby’s risk of NEC. However, donor milk is an important substitute or supplement if that isn’t available. Although pasteurization reduced antibody levels in donor milk, more research is needed to determine what levels of antibodies are protective against disorders such as NEC. In the future, researchers may be able to develop antibodies that may be given to formula or breast milk to improve protection by better knowing the specific bacteria that are most hazardous for preterm infants at risk of NEC.

In the future, researchers may be able to develop antibodies that may be given to formula or breast milk to improve protection by better knowing the specific bacteria that are most hazardous for preterm infants at risk of NEC.

The UPMC Children’s Hospital of Pittsburgh/R.K. Mellon Institute for Paediatric Research, the National Institutes of Health, and the March of Dimes funded this study.

Journal Reference:

1. Darryl A. Abbott, Kara E. Coffey, et al. Stability and heterogeneity in the anti microbiota reactivity of human milk-derived immunoglobulin A. Journal of Experimental Medicine. DOI: 10.1084/jem.20220839.