Pregnancy stage-dependent modulation of neutrophil function may impact embryo survivability and pregnancy outcome in crossbred cows.

Pregnancy is a complicated physiological process that involves synchronized coordination between immune and endocrine systems. Neutrophils have been suggested as a critical immune cell for embryo implantation and pregnancy maintenance. The present study was conducted to evaluate the dynamic changes in the mRNA expressions of the cluster of designation (CD11b, CD31, CD44 and CD62L) molecules and interferon-stimulated genes (ISG15, MX1 and OAS1) in blood neutrophils throughout pregnancy in dairy cows and correlate them with the outcome of pregnancy. Blood samples were taken from negative control (NC) group, and non-pregnant (NP) group at the time of artificial insemination (AI, day zero) and on days 10, 14, 16, 18, and 21 post-AI. In pregnant (P) cows, samples were taken as described above and after every 30 days until the time of parturition. In aborted cows, samples were collected until the time of the abortion. Comparison between pregnant, non-pregnant and aborted cows revealed that the expression of CD molecules increased (p < 0.05) on days 14, 16, 18 and 21 post-AI only in NP cows as compared to other groups. Although the expression of CD molecules remained constant throughout the study period in pregnant and aborted cows, the expression of CD11b, CD31 and CD62L increased (p < 0.05) on the day of abortion and parturition. Unlike CD molecules, the expression of CD44 decreased significantly (p < 0.05) at the time of abortion. There was a significant (p < 0.05) increase in the expression of interferon-stimulated genes including MX1, OAS1 and ISG15 during the peri-implantation period in pregnant cows, and at the time of abortion in aborted cows. However, the expression of ISGs was lower (p < 0.05) in non-pregnant cows as compared to the other groups. The results revealed the critical role played by neutrophils during pregnancy and form the basis to unravel the underlying mechanism for neutrophil associated immunological infertility in bovines.