A Macrophage is a white blood cell, produced by Monocytes. Monocytes and Macrophages are both Phagocytes. These work as a part of the human immune system. They act in non-specific "innate" immunity...
Murine means "of, related to, or affecting rodents of the family Muridae," like mice. Murine macrophages are simply macrophages of these types of animals.