The ‘Hatching’ of Reproductive Immunology

Transplantation immunology has progressed since Paul Bert's experiments on rats in the 19th century regarding the riddle of the mother's acceptance of an antigenically different fetus carrying paternal antigens. The modification of the pregnant female's immune reactivity became a topic developed by several research workers. Vera and Milan Hasek contributed largely to the field during the days and years of 'specific acquired tolerance' in the early 1950s, showing in particular that the pregnant mother was able to reject foreign and even paternal tissue grafts when transplanted to an ectopic site. Furthermore, fetal tissue was sufficiently immunogenic to elicit a rejection reaction when grafted on to a third party or maternal recipient. Therefore, attention was focused on local events linked to the placenta and trophoblast and to the hormonal balance during pregnancy. The long list of lymphokines and cytokines present in the vicinity of the implantation site and the crucial role of NK cells and their respective control represented topics aimed at an explanation of various types of failure of fetal development and abortions. It was soon clear that a large number of conditions and factors were involved in the chain of events during pregnancy, beginning at the early stages (e.g. EPF = early pregnancy factor). However, the lack of even one factor or step can lead to fetal demise.