CHARACTERIZATION OF CONCEPTUS-PRODUCED GOAT INTERFERON-TAU AND ANALYSIS OF ITS TEMPORAL AND CELLULAR-DISTRIBUTION DURING EARLY-PREGNANCY

Two proteins (17 and 22-24 kDa) produced by day 17 goat conceptuses we re purified from in vitro culture media. Analysis of their N-terminal amino acid sequences and of their antiviral activity confirmed that bo th proteins belonged to the interferon tau family characteristic of ru minant conceptuses. The two molecules were glycosylated (22-24 kDa) or nonglycosylated (17 kDa) isoforms of the same protein. The time cours e of secretion was plotted and immunoblotting of the protein contents of uterine flushings from day 13 to day 21 of pregnancy was performed. The nonglycosylated isoform (17 kDa) was first detected on day 16; bo th isoforms were present at day 17 and, thereafter during pregnancy, t he two proteins were not present in uterine flushings. Immunohistochem istry was used to show that the goat interferon tau was present in the trophoblastic cells as early as day 14 and until day 17. However, imm unostaining was not uniform along the conceptus; labelling was greater at the abembryonic pole than at the embryonic pole. By day 18, as imp lantation proceeded, goat interferon tau was no longer detected. These results confirmed that the goat conceptus secretes interferon tau dur ing the period of maternal recognition of pregnancy but its rapid decr ease suggests that other factors need to be present by day 18 to take over its role in the maintenance of luteal function.