Researchers in Australia have discovered how breastfeeding reshapes the immune system to provide long-term protection against breast cancer, particularly aggressive triple-negative types
Published in Nature, the study provides a biological explanation for the protective effect of childbearing and shows how this has a lasting impact on a woman’s immune system.
This was disclosed in a statement released on Tuesday by Australia’s Peter MacCallum Cancer Centre (Peter Mac), which led the study.
“We found that women who have breastfed have more specialised immune cells, called CD8⁺ T cells, that ‘live’ in the breast tissue for decades after childbirth,” said Prof. Sherene Loi.
Loi is the study’s lead author at Peter Mac.
“These cells act like local guards, ready to attack abnormal cells that might turn into cancer,” she said.
Loi added that this protection likely evolved to defend mothers during the vulnerable post-pregnancy period, and now also lowers breast cancer risk, especially aggressive triple-negative breast cancer.
Completing a full cycle of pregnancy, breastfeeding, and breast recovery caused these T cells to accumulate in the breast, Loi said, adding their protective effect was confirmed in preclinical experiments.
“When breast cancer cells were introduced, the models with this reproductive history were far better at slowing or stopping tumour growth, but only if T cells were present,” she said.
Data from over 1,000 breast cancer patients also indicated that women who breastfed had tumours with higher numbers of these protective T cells and better survival rates after diagnosis, researchers said.
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