Recognizes a protein of 21kDa, identified as human Placental Lactogen (hPL). hPL is known to originate in the syncytiotrophoblasts. Ultrastructural localization indicates that placental lactogen is stored in small morphologically distinct cytoplasmic granules within these cells and has a different secretory mechanism from other hormonal peptides such as human chorionic gonadotropin. Human placental lactogen gene expression in the placenta is very low in the first trimester of pregnancy and may not be detected by standard immunohistochemical methods. The level of expression of placental lactogen through pregnancy increases gradually to term. This antibody is useful for the detection of human placental lactogen in placenta and in cells showing trophoblastic differentiation eg in malignant testicular teratomas.