Short communication: Menaquinone-4 (vitamin K) induces proliferation responses in bovine peripheral blood mononuclear cells.

The effects of vitamin K (VK) on immune cells in ruminants are yet to be fully investigated. The objective of this study was to examine the effects of VK on peripheral blood mononuclear cells (PBMC) in Holstein dairy cows. A cell proliferation assay was performed to evaluate the effect of menaquinone-4 (MK-4, the biologically active form of VK) on immune response of PBMC. The proliferation of PBMC stimulated by MK-4 was significantly higher than that of nonstimulated controls. The expression of T cell-related genes in PBMC, stimulated with MK-4, was assessed by quantitative PCR. No significant changes were observed in the mRNA expression levels of both CD4 and CD8 as helper T cell and cytotoxic T cell markers, respectively. The present study demonstrated that MK-4 positively influenced cow PBMC proliferation and suggested the possibility of bovine-specific immune cell activation. The present study lays a foundation for understanding the physiological role of VK in cattle.