Immunology is a distinctive subject that rose in the mid-20th century. The subject developed as scientists started to unravel the mysteries about the defense system against pathogens. Researchers started to understand the mechanisms employed by the innate and the adaptive immune system in defense against pathogens. During the last decade, the subject of immunology has been in sharp focus as the immunotherapies against diseases like cancer and AIDS seems last hope. Employing the body's own defense system against diseases like cancer and AIDS by activating specific cells of the immune system looks promising, and therapies like CAR-T cell therapy have been approved. In the first edition of the book "The Fundamentals of Immunology" we have explained the basics of the defense system of our body. The book is organised into four volumes. The first volume comprises of ten chapters and it describes the rise, history and scope of immunology and the building blocks of the immune system viz., cells, molecules and organs of the immune system. The second chapter describes the cells of the innate and the adaptive immune system and how the granulocytes and macrophages employ defense mechanisms to protect the body against pathogenic invasions. In the third chapter of this book, we have described the organs of the immune systems and how different organs are involved in the differentiation and maturation of immune cells. The chapter also focused on the structure of lymph nodes and their function in concentrating the antigens. In chapter four of this book, we have described the terms like antigens, immunogens, antigenicity, immunogenicity and how immunogenicity of an antigen is affected and how antigenicity of an immunogens is related to the immune response. The innate and adaptive immune systems and the different types of cells and molecules employed by the two branches of immunity have been described in a separate chapter. The structure and biology of immunoglobulins, their types and function in antigen binding and antibody dependent cellular cytotoxicity (ADCC) have been described well in chapter six. Focus has been laid on the distinction between an antibody and an immunoglobulin. The structure and function and major histocompatibility complex (MHC) has been described. The education of cells about self and non-self during their maturation and the processing and presentation of antigens by MHC bearing cells and how MHC coordinates both humoral and cell-mediated immune responses has been explained well throughout the book. The book has explained the complement system and its components, mechanisms and functions in a separate chapter. At the end of the book, we have given an insight about the vaccines, their history, development and how they are useful and helpful in the defense against diseases. The book also discusses the immune disfunction and diseases associated with the dysregulation of immune responses.