In the mucosal microenvironment of the fallopian tube or the breast, prior to HGSOC or breast cancer development, PD-1, LAG3, TOX, TIGIT, and CD39 positive exhausted T cells and NK/NKT cells are significantly enriched in BRCA1/2 mutation carriers, indicating that the early adaptive immune responses are initiated, whereas T cells undergo a transformation towards an immune exhaustion phenotype. Here, LAG3 is linked to breast carcinoma.