Kazuhiko Imakawa

Suppression of T‐Lymphocyte Blastogenesis by Ovine Trophoblast Protein‐1 and Human Interferon‐α May Be Independent of Interleukin‐2 Production

ABSTRACT: Cells derived from the trophoblast tissue of a day 15 sheep conceptus released substances that inhibit incorporation of [3H]thymidine into phytohemagglutinin (PHA)‐stimulated ovine lymphocytes. This effect was partially reversed by addition of antiserum to ovine trophoblast protein‐1 (oTP‐1), a major secretory product of day 13–21 sheep conceptuses and a protein structurally and functionally related to α‐interferons (IFN‐α). Human IFN‐a, unlike dexamethasone, inhibits phytohemagglutinin‐induced lymphocyte blastogenesis without reducing interleukin‐2 (IL‐2) production by the cultures, and conditioned medium containing IL‐2 does not promote [3H]thymidine incorporation into ovine lymphocytes when oTP‐1 is present. Thus, oTP‐1, by virtue of being an IFN, may have a local immunomodulatory role by selectively inhibiting the proliferative responses of certain maternal immune cells to IL‐2.