Pre-term birth and severe pre-eclampsia are not associated with altered expression of HLA on human trophoblasts

PROBLEM: The unusual pattern of human leukocyte antigen (HLA) expression on human trophoblasts could play an important role in successful pregnancy outcome. To determine whether alterations in HLA expression are associated with pregnancy abnormalities we have investigated expression of these antigens on chorionic and extravillous cytotrophoblasts. METHODS: Frozen tissue sections of placenta and fetal membranes were collected after pre-term spontaneous delivery, severe pre-eclampsia pre-term Caesarean section, normal term delivery and term Caesarean section. HLA expression was analyzed by immunohistochemistry. RESULTS: We did not observe differences in the expression of HLA on chorionic and extravillous cytotrophoblasts in pregnancy abnormalities. However, we noted higher expression levels of HLA class Ia molecules in amnion epithelial cells in pre-term deliveries. Furthermore, in severe pre-eclampsia the number of extravillous cytotrophoblast islands were elevated when compared with pre-term deliveries. CONCLUSIONS: No alterations in expression of HLA class Ia, HLA-G and HLA class II on human trophoblasts in pregnancy abnormalities were seen.