Common denominators of pregnancy and malignancy

Antigenic tissue is paradoxically tolerated by a seemingly intact immune system in two biological situations, pregnancy and malignancy. Increasing evidence in recent years supports the idea that similar or identical immune mechanisms may be responsible for the tolerance of antigenic tissue in these two systems. What is apparently essential for the immunologic survival of the fetal allograft is detrimental for the patient with malignancy. This evidence is based on a number of common denominators, including such general observations as depression of cellular immunity, the presence of suppressive and/or blocking substances, embryogenization of neoplastic tissue, common lymphocyte populations and activities, and some specific in vitro observations, such as leukocyte migration enhancement (LME) and red cell immune adherence (RCIA). These common denominators of pregnancy and malignancy have been reviewed in detail and it is suggested that further understanding of one system will also contribute to our knowledge of the other.