Figure 1.

This figure illustrates the sequence of events that led to the discovery of interferon tau (IFNT) in ovine conceptus conditioned culture medium and identified in this figure of a two-dimensional polyacrylamide gel by green arrows. Details of how embryo transfer experiments contributed to discovery of pregnancy recognition signaling are provided in the text. Protein X, trophoblastin, ovine trophoblast protein 1, type 1 trophoblast interferon were names given the protein which was finally named interferon tau.