IFN-gamma induces aberrant CD49b(+) NK cell recruitment through regulating CX3CL1: a novel mechanism by which IFN-gamma provokes pregnancy failure

Interferon-gamma (IFN-gamma),a pleiotropic lymphokine,has important regulatory effects on many cell types. Although IFN-gamma is essential for the initiation of uterine vascular modifications and maintenance of decidual integrity, IFN-gamma administration can also cause pregnancy failure in many species. However, little is known about the effector mechanisms involved. In this study, using an IFN-gamma- induced abortion mouse model, we reported that no Dolichos biflorus agglutinin lectin-positive uterine natural killer (uNK) cells were observed in the uteri from IFN-gamma- induced abortion mice. By contrast, the percentage of CD3(-) CD49b(+) NK cells in the uterus and blood from a foetal resorption group was significantly higher than that of the control group. Similarly, significantly upregulated expression of CD49b (a pan-NK cell marker), CX3CL1 and CX3CR1 (CX3CL1 receptor) was detected in the uteri of IFN-gamma-induced abortion mice. Using isolated uterine stromal cells, we showed that upregulated expression of CX3CL1 by IFN-gamma was dependent on a Janus family kinase 2-signal transducers and activators of transcription 1 (JAK2-STAT1) pathway. We further demonstrated the chemotactic activity of CX3CL1 in uterine stromal cell conditioned medium on primary splenic NK cells. Finally, we observed increased recruitment of CD49b(+) NK cells into the endometrium after exogenous CX3CL1 administration. Collectively, our findings indicate that IFN-gamma can significantly increase uterine CX3CL1 expression via activation of the JAK2-STAT1 pathway, thus inducing CD49b(+) NK cell uterine homing, and eventually provoke foetal loss. Thus, we provide a new line of evidence correlating the deleterious effects of IFN-gamma on pregnancy with the aberrant regulation of CX3CL1 and CD49b(+) NK cells.