Neutrophil gene dynamics and plasma cytokine levels in dairy cattle during peri-implantation period.

Neutrophils being the first line of cellular defense show significant difference in their expression in pregnant (P) and non-pregnant (NP) cows during the peri-implantation period. To study these changes, blood samples were collected from cows coming in heat and brought for artificial insemination (AI) on day 0 (day of AI), 4, 8, 12, 14, 16, 18, 21, 24, 30 and 40 day post-AI. Pregnancy was confirmed by observing non-return of heat, progesterone assay and ultrasonography. Cows were then categorized into pregnant (n=10) and non-pregnant (n=10) groups. Blood neutrophils were isolated and plasma samples collected from both P and NP cows during this period. RNA from neutrophils was isolated and studied for gene expression of adhesion molecules (CD62L, CD11b), chemokine (IL-8), and interferon stimulated genes (ISG15, OAS1, MX1, MX2, IFI16 and IFI44) using qRT-PCR. Adhesion molecules along with IL-8 showed a higher expression in NP cows. Expression of IFI16 was up-regulated as early as day 8, whereas, that of ISG15, OAS1, MX1 and MX2 were up-regulated on days 12-21 post-AI in P cows. Highest expression was shown by OAS1 on day 18 and by ISG15 and MX2 on day 21 post-AI in P cows. Pro-inflammatory cytokines (TNFα and IL-8) were higher, whereas, anti-inflammatory cytokine (IL-10) levels were lower in plasma samples isolated from NP cows. Our study indicates that blood neutrophils are sensitive to implantation signals received from the conceptus and may play an important role in implantation of the developing conceptus.