Interferon tau is a Type I interferon made up of a single chain of amino-acids.
In many species of ruminant, it acts as a signaling molecule during pregnancy. It is secreted by the trophoblast cells into the uterine lumen in days 13-21 of pregnancy. It decreases endometrial oxytocin receptors, which then cannot stimulate PGF-2-alpha synthesis, preventing luteolysis. It promotes uterine implantation by increasing protein synthesis in glands. Although its role in humans is not certain, it has been found to bind to the same receptors sensitive to interferon alpha, and thus may have anti-viral properties, as hinted by studies showing its ability to inhibit the reverse transcriptase enzyme found in retroviruses such as HIV. Its low toxicity compared to other interferons also supports its investigation as a potential therapeutic compound.