Investigating the functional capacity of porcine uterine natural killer cells during a porcine reproductive and respiratory syndrome virus infection of pregnant gilts.

Uterine natural killer (uNK) cells play crucial roles in pregnancy, impacting maternal-fetal immune tolerance, angiogenesis, and immune responses. While extensively studied in humans and mice, porcine uNK cells' functional properties remain relatively underexplored in both healthy uterine environments, as well as during viral infection. This study examined the functional properties of porcine uNK cells isolated from the maternal endometrium (ME) and fetal placenta (FP) in late gestation, comparing healthy gilts to those experimentally infected with porcine reproductive and respiratory syndrome virus (PRRSV), one of the most economically damaging reproductive viruses of the swine industry. Flow cytometry analyses identified three uNK cell subsets based on NKp46 expression to assess subpopulation frequencies and functional variations. Results showed that PRRSV infection did not significantly alter the total NK cell counts but affected NK cell proliferation. NKp46high subsets showed increased Ki-67 expression in samples from experimentally infected gilts. An upregulation of perforin was observed in NKp46high cells, indicating potential immune responsiveness to PRRSV. CD107a degranulation capacity of the examined NK cells was lower in FP uNK cells, possibly due to the fetal immune environment's immaturity. Despite PRRSV exposure, CD107a expression did not significantly change in uNK cells. PRRSV infection led to a suppression of interferon (IFN)-γ expression in most uNK cell subsets. This study provides a look into a previously unstudied aspect of the immune response to PRRSV infection in the porcine uterus and gives new insights into porcine NK cell subsets in an important non-lymphoid organ.