IFN-delta

Interferon-delta (IFN-δ) is a type I interferon found in pigs and ruminants, absent from humans and rodents, with its most distinctive role in reproductive biology. IFN-δ is co-expressed with IFN-τ (in ruminants) or on its own (in pigs, where no functional IFN-τ exists) by the peri-implantation trophoblast; in the pig, IFN-δ is the principal maternal pregnancy recognition signal, secreted by elongating conceptuses between days 11 and 15 of gestation to attenuate endometrial prostaglandin F2α release and maintain luteal function. The porcine IFN-δ proteins, encoded by multiple gene copies, are about 150 amino acids in size, share limited homology with IFN-α (~35%), and signal through the universal IFNAR1/IFNAR2-JAK-STAT pathway, exerting classical antiviral activity in endometrial and immune cells. IFN-δ also contributes to the establishment of local uterine immune tolerance and angiogenesis, illustrating the recurrent evolutionary recruitment of interferons to viviparous reproduction.