Detection of trophoblast-like cells in maternal blood using specific monoclonal antibodies.

Mouse monoclonal antibodies reacting against membrane antigens expressed on syncytiotrophoblast (McAb H315), villous cytotrophoblast (McAb 18B/A5) and placental-type alkaline phosphatase-producing cells (McAb H317) were used in conjunction with flow cytometry to detect placental cells in the maternal circulation. H315 and H317-positive cells were found in uterine veins and peripheral blood of pregnant women, while cells reacting with McAb 18B/A5 were either absent or present in very low numbers.