Breast milk contains antibodies, especially a type called immunoglobulin A or IgA, that prevent gastrointestinal problems and promote survival and well-being in infants. A new study led by Tomonori Nochi at Tohoku University in Japan, with Professor Russell Hovey at the UC Davis Department of Animal Science, shows how microbes in the gut are connected to IgA in breast milk.

“We still lack a complete picture when it comes to antibody production in lactating mothers, and this has hindered the discovery of immunological and microbiological approaches to increasing breastfeeding quality,” Nochi said.

The researchers worked with mice, including mice maintained in germ-free environments where they could manipulate their gut microbe population.

They found that the cells that produce IgA in breast milk originate in immune structures in the gastrointestinal tract called Peyer’s Patches.

Bacteria promote antibodies

They also identified two types of bacteria, Bacteroides acidifaciens and Prevotella buccalis, which live in the gastrointestinal tract of mothers and generate immune responses that result in IgA-producing plasma cells that migrate to the mammary gland.

Knowing the source of the IgA allows researchers to explore questions such as whether these antibodies can be enhanced in mother’s milk, the development of probiotics that build maternal immunity, and whether certain diseases seen in mothers can be reduced or prevented.

The work was published Sept. 7 in Cell Reports. Additional authors are: Katsuki Usami, Kanae Niimi, Ayumi Matsuo, Yoshihisa Suyama, Yoshifumi Sakai, Saeka Uchino, Mutsumi Furukawa, Jahidul Islam, Kaori Ito, Hiroshi Yoneyama, Haruki Kitazawa, Kouichi Watanabe, Hisashi Aso and Junichi Sugawara, Tohoku University; Shintaro Sato, Osaka University; Kohtaro Fujihashi, Hiroshi Kiyono, University of Tokyo; Taiki Moriya, Yutaka Kusumoto and Michio Tomura, Osaki Ohtani University.