The fetal antigen hypothesis for breast cancer, revisited.

The fetal antigen hypothesis was proposed over a decade ago to explain the small, short-term promotional effect, as well as part of the long-term protective effect that pregnancy has on breast cancer risk. The hypothesis is based on immune interaction between mother and fetus, and postulates that breast cancer genes which a women's fetus inherits from her mate may be indirectly involved in protecting the woman against breast cancer. This article addresses new epidemiological data pertaining to the hypothesis plus the growing evidence that prenatal reproductive factors are important determinants of breast cancer risk. It also suggests that iso-immunization from pregnancy, similar to Rh iso-immunization, can produce immunity against breast cancer. The proposed mechanism provides a plan for development of a vaccine against breast cancer. If the fetal antigen hypothesis is valid for breast cancer, the mechanism behind it is likely to apply to other cancers, even cancers that are found in males, since males can be affected be the prenatal component of this mechanism.