Cells that travel from the intestine to the breast: how a woman's body changes to protect her child through breastfeeding.

BarcelonaA woman's immune system changes during pregnancy and breastfeeding, which has benefits for both the pregnant woman and the baby. When a mother breastfeeds, she reduces the risk of breast cancer, ovarian cancer, type 2 diabetes, and high blood pressure. It also supports the nutrition and immune system of the newborn. Although science is widely aware of the positive effects of breastfeeding, the reasons behind it are still unknown. Now, researchers in the United States have discovered in a study that there are abundant immune cells in the mammary glands, some of which come from the mother's intestine and promote better health for both her and her child.

The authors of the research published this Tuesday in the journal Nature Immunology They are immunologists at the Salk Institute in San Diego who have mapped the migration of immune defenses before and during breastfeeding. They used mice and also breast milk samples and believe their findings may help explain the benefits of breastfeeding, drive new solutions for mothers who cannot breastfeed, and guide dietary choices that improve milk production and quality.

Thus, they have discovered that during breastfeeding "there is a significant increase in immune cells in breast tissue, and that this increase requires the presence of microbes," explains researcher and lead author of the study, Deepshika Ramanan. Until now, previous studies focused on the relationship between breast milk content and the baby's health. It was known that newborns receive important intestinal bacteria and antibodies, but the changes a woman's body undergoes during this period were unknown.

Some of the many immune cells they found in the mammary glands are called intraepithelial lymphocytes and are found in mucosal tissues of the intestines or lungs, which are exposed to the outside world through food and air. This makes these tissues more vulnerable, so they have special defenses that are ready to act against any threat. The migration of these cells from the intestine to the breast facilitates the mammary gland's transition from non-mucous to mucous tissue and prepares it for lactation, at which point it will be exposed to the outside world, in addition to the microbes on the mother's skin and the baby's mouth.

Solutions for mothers who cannot breastfeed

Understanding the changes in maternal immune cells during pregnancy and breastfeeding could have a "generational impact," as immune and microbiome transfers from mother to child occur constantly, the authors argue. The findings could also lead to solutions for mothers who are unable to breastfeed, either through therapies that help stimulate natural milk production or more sophisticated formulas that offer similar immune support. As the connection between the gut and the mammary gland is further explored, the researchers believe that future recommendations for diets may be possible to promote breast and maternal health and optimize milk quality.

"We now know much more about how the maternal immune system changes during this critical period and can begin to explore the direct effects of these immune cells on the health of both mother and baby," says Ramanan, who believes that much research remains to be done. "If we're seeing a connection between the gut and the mammary gland, what other interactions might be happening in the body? And what else might be affecting the milk we pass on to our children?" she concludes.