Expression of retrovirus-related antigen in pregnancy. I. Antigens cross-reacting with simian retroviruses in human foetal tissues and cord blood lymphocytes.

Antisera to Mason-Pfizer or Baboon Endogenous Virus possessed complement-dependent cytotoxicity for cell lines chronically infected with these viruses, with some degree of cross-reaction. When appropriately absorbed with virus-free cells, the antisera were not cytotoxic for lymphocytes of adult males but lysed lymphocytes of neonates in about half of the 30 cord blood samples tested and were also cytotoxic for one third of 26 trophoblast suspensions prepared from healthy placentae. Detection of retrovirus-related antigens was no more frequent in trophoblast from 9 pre-eclamptic placentae. These viral antigens were also demonstrated in cultures of foetal tissues, but only after a period of culture and only when the cells were treated with 5-iododeoxyuridine. The results demonstrate that retroviruses are not only expressed in vivo in the placenta but can also be induced in cultures of foetal cells. Retrovirus-related antigens also seem to be present on foetal lymphocytes.