The oral mucosal immune system acts as the "gateway to the gut"; it must recognize and eliminate pathogens, while tolerating harmless commensals. This ability to discriminate friend from foe is without question the most important property of the immune system and essential for maintaining immune homeostasis. Dendritic cells (DC) are immune cells which may well represent a "first line" of sensitization of the immune system, leading to clearance of the antigen or to a pathological phenomena. This book highlights the role of dendritic cells in the pathogenesis of oral pathological entities and also lays special emphasis on their role in immunoregulation including the use of dendritic cells as critical adjuvant in vaccine for prevention of microbial infection and allograft rejection and also in treatment of cancer.