Cold Spring Harbor Laboratory scientists have discovered that after pregnancy, breast cells call in natural killer T (NKT) cells to prevent tumors from arising. This finding—published in Cell Reports, illuminates a new way in which pregnancy reduces the risk of breast cancer.
Researcher Amritha Varshini Hanasoge Somasundara says that in post-pregnancy, “There is an increase in this specific cell type, and only in the mammary gland. We don’t see the expansion everywhere else in the body, even though NKT cells are present everywhere else in the body.”
The team wanted to know what the larger number of NKT cells were doing in the breast tissue. They discovered that in mice, breast epithelial cells produce a specific protein called CD1d after pregnancy. If the cells did not present CD1d, the researchers observed no increase in NKT cells in the tissue; the epithelial cells became cancerous and grew into tumors. The scientists suspect that CD1d molecules are calling in NKT cells to monitor the epithelial cells in the breast tissue after pregnancy. If they become cancerous, the NKT cells can quickly kill them to prevent tumor growth.
Lead researcher Camila Dos Santos concludes, “One of the hypotheses that we are working on now is: do pregnancies later on in life bring in the same expansion of the same subtypes of immune cells as pregnancies that took place early in life?”