A monoclonal antibody to human placental lactogen hormone facilitates isolation of fetal cells from maternal blood in a model system.

A cocktail of trophoblast-reactive monoclonal antibodies (MAbs) is required for efficient isolation of trophoblasts from maternal blood. A modified antibody screening procedure was used to identify a clone, in a COS cell placental cDNA expression library, that expressed the gene product recognized by MAb FDO202N. The antigen recognised by MAb FDO202N was identified as human placental lactogen (hPL) hormone. hPL hormone is secreted into the maternal blood by trophoblasts at high levels during pregnancy. Immunohistochemical localization of hPL hormone was consistent with expression in the syncytiotrophoblast and extravillous cytotrophoblast. A model system was used where known numbers of syncytiotrophoblast sprouts were seeded into saline or maternal blood, bound by trophoblast-specific MAbs, recovered magnetically, and then counted. MAb FDO202N was shown to facilitate the efficient recovery of trophoblast sprouts from saline and maternal blood.