Overview
- Analysis of more than 260 non‑cancer breast tissue samples found higher densities of specialised CD8+ T cells in women who had breastfed, with cells persisting for decades.
- Mouse experiments showed that completing a full pregnancy–lactation–involution cycle slowed tumour growth and boosted T‑cell infiltration, while depleting T cells removed this protection.
- Clinical data from over 1,000 women with triple‑negative breast cancer linked prior breastfeeding to better survival and higher tumour T‑cell density.
- Researchers propose that microbial exposures and mastitis during breastfeeding may recruit these immune cells to breast tissue, a hypothesis now guiding mechanistic studies.
- The findings reframe hormone‑centric explanations and point to preventive strategies that could mimic this immune protection, while underscoring that breastfeeding does not guarantee cancer avoidance.