Emerging Questions in Materno-Fetal Microchimerism

Naoki Irie\r\n

Abstract

Materno-fetal microchimerism is a common, life-long chimeric state first established by the exchange of small numbers of cells between the mother and the fetus during pregnancy. This apparently trivial phenomenon is now attracting attention due to its unexpected and profound implications in the immune system. For example, is the placenta really an immunological barrier? How do we balance the internal environment despite the existence of an immunological non-self? In this review, I will discuss the pros and cons of materno-fetal microchimerism for our immune system (e.g., tolerance, materno-fetal immune disease, tissue regeneration, etc.) and the unanswered, puzzling aspects of microchimerism from the immunological point of view.\r\n