{"id":54054,"date":"2025-07-29T08:00:21","date_gmt":"2025-07-29T15:00:21","guid":{"rendered":"https:\/\/www.salk.edu\/?post_type=disclosure&p=54054"},"modified":"2025-07-29T10:30:39","modified_gmt":"2025-07-29T17:30:39","slug":"how-does-the-immune-system-prepare-for-breastfeeding","status":"publish","type":"disclosure","link":"https:\/\/www.salk.edu\/de\/news-release\/how-does-the-immune-system-prepare-for-breastfeeding\/","title":{"rendered":"How does the immune system prepare for breastfeeding?"},"content":{"rendered":"

LA JOLLA\u2014Of the 3.6 million babies born in the United States each year, around 80 percent begin breastfeeding in their first month of life. Breastfeeding has known benefits for both mother and child, reducing maternal risk of breast and ovarian cancers, type 2 diabetes, and high blood pressure, while simultaneously supporting the baby\u2019s nutrition and immune system. But because pregnancy and lactation have been historically understudied, we still don\u2019t understand the science behind many of these benefits.<\/p>\n

\"Virgin<\/a>
Virgin (left) and lactating (right) mouse mammary gland imaging shows the dramatic structural changes that occur to facilitate milk production, including cell proliferation and the formation of milk ducts.
Klicken Sie hier<\/a> f\u00fcr ein hochaufl\u00f6sendes Bild.
Kredit: Salk Institut<\/figcaption><\/figure>\n

Salk Institute immunologists are changing that\u2014starting with a map of immune cell migration before and during lactation. Using both animal research and human milk and tissue samples, the researchers discovered that immune cells called T cells are abundant in the mammary glands during pregnancy and breastfeeding, with some relocating from the gut. These cells likely support both maternal and infant health.<\/p>\n

The findings, published in Nature Immunology<\/em><\/a> on July 29, 2025, may help explain the advantages of breastfeeding, prompt new solutions for mothers unable to breastfeed, and inform dietary decisions that enhance breast milk production and quality.<\/p>\n

\u201cBy investigating how immune cells change during pregnancy and lactation, we were able to find lots of exciting things\u2014notably, that there\u2019s a significant increase in immune cells in mammary tissue during lactation, and the increase in immune cells requires microbes,\u201d says Assistant Professor Deepshika Ramanan<\/a>, senior author of the study.<\/p>\n

What we know: Babies get gut bacteria and antibodies from mother\u2019s milk<\/strong><\/p>\n

Most breastfeeding studies focus on the relationship between milk content and infant health. These studies, including previous work by Ramanan, have shown that babies receive important gut bacteria and antibodies from their mother through the breast milk, which lays a critical foundation for their developing immune system. Still, much less is known about the changes to the mother\u2019s body during this time.<\/p>\n

Some features of the mammary gland immune landscape can be inferred from milk content research. For example, the presence of antibodies in breast milk means that antibody-producing immune cells called B cells must be present. But few have looked directly at immune cell activity within the mammary gland itself.<\/p>\n

What\u2019s new: Mom\u2019s gut microbes boost immune cells in mammary glands<\/strong><\/p>\n

\u201cWhat\u2019s really exciting is that we didn\u2019t just find more T cells in mammary glands, we found that some of these T cells were actually coming from the gut,\u201d says first author Abigail Jaquish, a graduate student researcher in Ramanan\u2019s lab. \u201cWe think they are likely supporting mammary tissue in the same way they typically support intestinal tissue.\u201d<\/p>\n

\"From<\/a>
From left: Abigail Jaquish and Deepshika Ramanan.
Klicken Sie hier<\/a> f\u00fcr ein hochaufl\u00f6sendes Bild.
Kredit: Salk Institut<\/figcaption><\/figure>\n

The researchers began their study by looking at mouse mammary gland tissues at various stages pre- to post-lactation. By comparing these samples, they discovered that three different types of T cells were growing in number: CD4+, CD8\u03b1\u03b1+, and CD8\u03b1\u03b2+ T cells.<\/p>\n

This was curious to the team, because these T cell subtypes are members of a special immune cell class called intraepithelial lymphocytes. Intraepithelial lymphocytes live in mucosal tissues\u2014soft tissues like the intestines or lungs that are exposed to substances from the outside world. Because these tissues are more vulnerable, intraepithelial lymphocytes act as \u201cresident” immune cells, stationed on-site and ready for action.<\/p>\n

The researchers noticed these CD4+, CD8\u03b1\u03b1+, and CD8\u03b1\u03b2+ T cells were lining the mammary epithelium the same way they would line the epithelium of other mucosal tissues. What\u2019s more, these T cell subtypes bore gut-resident surface protein fingerprints\u2014pointing to T cell migration between the intestines and mammary glands. Together, these changes were facilitating a mammary gland transition from non-mucosal to mucosal tissue in preparation for lactation, where it would become exposed to the outside environment, including microbes from the mother\u2019s skin and the infant\u2019s mouth.<\/p>\n

But was this also happening in humans? An investigation into databases of human breast tissue and milk samples from the Human Milk Institute at UC San Diego revealed yes\u2014<\/em>human equivalents of these intraepithelial lymphocytes showed the same trends.<\/p>\n

The team returned to the mouse model with one final question: Are these mammary gland T cells impacted by microbes the same way they would be in the gut? They compared the mammary glands of mice living in normal and germ-free environments and found that all three T cells subtypes were expressed far more in mice exposed to microbes. This finding suggests that maternal microbes modulate the number of T cells created during lactation, which in turn could impact the strength of the mammary gland immune barrier.<\/p>\n

Altogether, T cell production ramped up with the help of microbes, T cells relocated from the gut to mammary glands, and the mammary glands switched from non-mucosal to mucosal tissues.<\/p>\n

Looking ahead: What affects this gut-breast immune axis, and thus influences our health for generations?<\/strong><\/p>\n

\u201cWe now know so much more about how the maternal immune system is changing during this critical time,\u201d says Ramanan, \u201cand we can now use this information to start exploring the direct effects of these immune cells on both maternal and infant health.\u201d<\/p>\n

The researchers hypothesize that hormones influence these many changes, and that the overall goal is protecting the mother from the outside world and related infection. But how they influence lactogenesis, milk quality, and maternal and baby health is the next case to crack.<\/p>\n

\u201cThere\u2019s so much more research to be done in this area\u2014we\u2019re just getting started,\u201d adds Jaquish. \u201cIf we\u2019re seeing a connection between the gut and the mammary gland, what other interactions might be happening in the body? And what else could be impacting the milk that we\u2019re passing on to our offspring?\u201d<\/p>\n

Understanding maternal immune cell changes during pregnancy and lactation can impact generations, as mother to child immune and microbiome transfers occur again and again<\/em>. The insights may also lead to solutions for mothers who cannot breastfeed, either with therapies that help support natural milk production or with more sophisticated formulas that provide some of the same immune support. As the connection between the gut and mammary gland becomes clearer, scientists could one day suggest diets to promote mammary and maternal health, as well as optimize milk quality.<\/p>\n

Other authors include Eleni Phung and Isabelle Bursulaya of Salk; Xutong Gong, Silvia Galvan-Pena, Ian Magill, Diane Mathis, and Christophe Benoist of Harvard Medical School; Pilar Baldominos, Eleonara Marina, and Judith Agudo of Dana-Farber Cancer Institute; Kerri Bertrand and Christina Chambers of UC San Diego; Andr\u00e9s R. Mu\u00f1oz-Rojas of Rensselaer Polytechnic Institute; and ImmgenT consortium members.<\/p>\n

The work was supported by the Damon Runyon Dale F. Frey Award, UC San Diego PiBS T32, National Institutes of Health (RO1-AI150686, R24-072073, NCI CCSG P30 CA014195, NIA San Diego Nathan Shock Center P30 AG068635, NCI CCSG: P30 CA01495, S10 OD023689, S10 OD034268), Chapman Foundation, and Helmsley Charitable Trust.<\/p>","protected":false},"featured_media":54064,"template":"","faculty":[418],"disease-research":[122],"class_list":["post-54054","disclosure","type-disclosure","status-publish","has-post-thumbnail","hentry","faculty-deepshika-ramanan","disease-research-immune-system-biology"],"acf":[],"yoast_head":"\nHow does the immune system prepare for breastfeeding? - Salk Institute for Biological Studies<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.salk.edu\/de\/news-release\/how-does-the-immune-system-prepare-for-breastfeeding\/\" \/>\n<meta property=\"og:locale\" content=\"de_DE\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How does the immune system prepare for breastfeeding? - Salk Institute for Biological Studies\" \/>\n<meta property=\"og:description\" content=\"LA JOLLA\u2014Of the 3.6 million babies born in the United States each year, around 80 percent begin breastfeeding in their first month of life. 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