Periodontal diseases are a multifactorial disease that encompasses the hard & soft tissue, microbial colonisation, inflammatory response and adaptive immune response.The complexity of the local tissue components, including bacteria and or their products & virtually all aspects of host response mechanisms, has complicated our ability to elucidate the critical protective functions in the tissues and has continually provided evidence for the potential for host destructive factors as the ultimate causative parameters in the disease.Rapid progress in immunobiology, more information about the role of the host in periodontal disease, coupled with recent advances in biotechnology, should lead to a better understanding of the pathogenesis of periodontal disease and provide diagnostic and prognostic aids.This book is an attempt to understand the basic concepts of immunology and its role in host response strategies periodontal diseases.