The expression of major histocompatibility antigens in the chorionic villi of molar placentae.

Frozen sections of chorionic villi from molar placentae, ranging in menstrual age from 9 to 19 weeks, were studied by an immunoperoxidase technique using the monoclonal antibody to HLA-A,-B,-C antigens W6/32. The distribution of class I HLA antigens in molar placentae was compared with that in normal placental tissue of comparable menstrual age. The results showed that the distribution of these antigens in molar placentae is similar to that seen in normal placentae. In both tissues, class I HLA antigens were absent from the syncytiotrophoblast and the cytotrophoblast cells of the chorionic villi. However, these antigens were found to be present on cells in the mesenchymal stroma of both normal and molar chorionic villi.