The topics addressed in this book firstly highlights the concepts of basic immunology which helps us in understanding the immune system of our body. The immune system is a system of many biological structures and processes within an organism that protects against disease. To function properly, an immune system must detect a wide variety of agents, known as pathogens, from viruses to parasitic worms, and distinguish them from the organism's own healthy tissue. Secondly, the book highlights each aspect of oral defense mechanism with easy detailing in different chapters for better understanding of the concepts. Role of Saliva, gingiva and its periodontium and oral mucosa in provinding immunity is emphasized in this book in detailed manner with pictorial and schematic diagrams wherever necessary.