Bovine granulocyte chemotactic protein-2 is secreted by the endometrium in response to interferon-tau (IFN-τ)

Interferon-tau (IFN-τ) is secreted by the bovine conceptus and may regulate synthesis of uterine endometrial cytokines to provide an environment that is conducive to embryo development and implantation. Interferon-τ stimulates secretion of an 8-kDa uterine protein (P8) in the cow. P8 was purified, digested to yield internal peptides, and partially sequenced to determine identity. Two internal peptides had 100% (13-mer) and 92% (12-mer) amino acid sequence identity with bovine granulocyte chemotactic protein-2 (bGCP-2). Bovine GCP-2 is an α-chemokine that acts primarily as a potent chemoattractant for granulocyte cells of the immune system. A peptide was synthesized based on a region of bGCP-2 that overlapped with a P8 peptide amino acid sequence, coupled to keyhole limpet hemocyanin, and used to generate high titer polyclonal antiserum in sheep. Western blots revealed that bGCP-2 was not released by endometrium from day 14 nonpregnant cows, but was released in response to 25 nM IFN-τ (p<0.05). Uterine GCP-2 exhibited high affinity to heparin agarose, a characteristic shared by all α chemokines. This is the first report describing presence of GCP-2 in the uterine endometrium and regulation by IFN-τ. The regulation of bGCP-2 by IFN-τ may have important implications for cytokine networking in the uterus during pregnancy. Also, the regulation of inflammation and angiogenesis by bGCP-2 working together with other cytokines may be integral to establishing early pregnancy and implantation in the cow.