Abstract
51chromium-labeled syncytiotrophoblasts purified from human placentae were lysed by allogenic leukocytes in vitro. The extent of syncytiotrophoblast lysis was dependent upon the dose of the leukocytes, occurred after a lag period of 42 h, and was inhibited by excess of unlabeled syncytiotrophoblasts. Autologous leukocytes failed to lyse syncytiotrophoblasts. Neuraminidase pretreatment of the syncytiotrophoblasts significantly enhanced their lysis by leukocytes. HCG failed to influence the extent of lysis of untreated syncytiotrophoblasts but significantly reduced the lysis of neuraminidase-treated targets. The significance of these observations in relation to the “immunologic privilege” of the tropho-blast in vivo is discussed.