Macrophages may also play a detrimental role. An overwhelming body of literature has indicated their crucial role in pathogenesis. The list includes sepsis, cancer, metabolic syndrome, immunodeficiency, auto-immune disease- virtually impacting every major pathology that we know. These observations have suggested macrophages and their related molecules as potential targets in therapeutic applications. Available evidence proclaims macrophages as a key player in homeostasis, host defense and disease. Crucial developments in the past few years call for a re-evaluation and update of our understanding of macrophages. The present book is an endeavour that attempts to provide state-of-the art knowledge of these cells in health and disease.