How might pregnancy immunize against breast cancer?

PROBLEM: This study investigated how pregnancy might protect against breast cancer. METHOD OF STUDY: A critical review of the literature was done. RESULTS/CONCLUSIONS: Support for an active role in pregnancy immunizing against breast cancer comes from case studies demonstrating a reciprocal correlation between pregnancy and breast cancer as well as recent experiments supporting the fetal antigen hypothesis that confirms the presence of a tumor-specific antigen, MUC1, on both fetal and breast cancer tissues. Multiparous women also generate anti-MUC1 major histocompatibility complex-restricted cytotoxic T cell cytolytic activity against MUC1-bearing tumor cell lines. Careful investigation of the fetal antigen hypothesis and tolerogenic mechanisms may lead to effective vaccination protocols against breast cancer and other cancers.