Immunology at the Maternal-Fetal Interface

Already very early after fertilization, there is direct contact between the blastocyst and the maternal decidua. From those very early days onward the immunological balance between mother and fetus has to be established and maintained as there is no doubt that the maternal immune system is certainly able to recognize the paternal antigens inherited by the fetus.9,10 The lack of a destructive immune response mounted by the mother seems to be related to the presence of an active immune process essential for normal pregnancy. This concept is supported by findings that an increase in the number of HLA differences between mother and child reduces the chance of getting certain complications of pregnancy. Sharing of HLA between mother and fetus is associated with increased incidence of pre-eclampsia and fetal growth retardation. This was confirmed by others, suggesting that in women with a history of pre-eclampsia an unusually high degree of immunological compatibility with the fetus was found.11-13 HLA-DR sharing between pre-eclamptic women and their partners is a risk factor for pre-eclampsia14 and is also associated with a reduced birth weight, on average 200 g less.15Supporting this hypothesis is the observation that with more maternal-fetal HLA class II disparities, an improvement in rheumatoid arthritis during pregnancy and in the period thereafter was found.16 This