Immunology. Richard Coico
cells, which leads to immunological deficiency and renders the patient powerless to resist infections by microorganisms that are normally benign. An important form of regulation concerns the prevention of immune responses against self‐antigens. As discussed in Chapter 12, this regulation may be defective, thus causing an immune response against self to be mounted. This type of immune response is termed autoimmunity and is the cause of diseases such as some forms of arthritis, thyroiditis, and diabetes, which are very difficult to treat.
THE FUTURE OF IMMUNOLOGY
For the student, a peek into the world of the future of immunology suggests many exciting areas in which the application of molecular and computational techniques promises significant dividends. To cite just a few examples, let us focus on vaccine development and control of the immune response. In the former, rather than the laborious, empirical search for an attenuated virus or bacterium for use in immunization, it is now possible to use pathogen‐specific protein sequence data and sophisticated computational methods (bioinformatics) to identify candidate immunogenic peptides that can be tested as vaccines. Alternatively, DNA vaccines involving the injection of DNA vectors that encode immunizing proteins may revolutionize vaccination protocols in the not too distant future. The identification of various genes and the proteins or portions thereof (peptides) that they are encoding makes it possible to design vaccines against a wide spectrum of biologically important compounds.
Another area of great promise is the characterization and synthesis of cytokines that enhance and control the activation of various cells associated with the immune response as well as with other functions of the body. Techniques of gene isolation, clonal reproduction, the polymerase chain reaction, and biosynthesis have contributed to rapid progress. Powerful and important modulators have been synthesized by the methods of recombinant DNA technology and are being tested for their therapeutic efficacy in a variety of diseases, including many different cancers. In some cases, cytokine research efforts have already moved from the bench to the bedside with the development of therapeutic agents used to treat patients.
Finally, and probably one of the most exciting areas, is the technology to genetically engineer cells and even whole animals, such as mice, that lack one or more specific traits (gene knockout) or that carry a specific trait (transgenic). These and other immune‐based experimental systems are the subject of the final chapter (Chapter 20). They allow the immunologist to study the effects of such traits on the immune system and on the body as a whole with the aim of understanding the intricate regulation, expression, and function of the immune response, and with the ultimate aim of controlling the trait to the benefit of the individual. Thus our burgeoning understanding of the functioning of the immune system, combined with the recently acquired ability to alter and manipulate its components, carries enormous implications for the future of humankind.
THE SHORT COURSE BEGINS HERE
This brief overview of the immune system is intended to orient the reader about the complex yet fascinating subject of immunology. In the following chapters we provide a more detailed account of the workings of the immune system, beginning with its cellular components, followed by a description of the structure of the reactants and the general methodology for measuring their reactions. This is followed by chapters describing the formation and activation of the cellular and molecular components of the immune apparatus required to generate a response. A discussion of the control mechanisms that regulate the scope and intensity of immune responses completes the description of the basic nature of immunity. Included in this section of the book is a chapter on cytokines (Chapter 11), the soluble mediators that regulate immune responses and play a significant role in hematopoiesis. Next are chapters that deal with the great variety of diseases involving immunological components. These vary from ineffective or absent immune responses (immunodeficiency) to those produced by aberrant immune responses (hypersensitivity) to responses to self‐antigens (autoimmunity). This is followed by chapters that describe the role of the immune response in transplantation and discuss antitumor reactions. Chapter 19 focuses on the spectrum of microorganisms that challenge the immune system and how immune responses are mounted in a vigilant, orchestrated fashion to protect the host from infectious diseases. Included is a discussion of immunoprophylaxis using vaccines that protect us from variety of pathogenic organisms. Without question, the successful use of vaccines helped revolutionize the field of medicine in the twentieth century. What lies ahead in the twenty‐first century are research efforts related to the development of crucial new vaccines to protect humankind from naturally occurring pathogenic microorganisms and viruses (most notably HIV and the novel coronavirus responsible for the recent COVID‐19 pandemic), as well as those that have been engineered as potential biological weapons, or have yet to be identified.
With the enormous scope of the subject and the extraordinary richness of detail available, we have made every effort to adhere to fundamental elements and basic concepts required to achieve an integrated, if not extensive, understanding of the immune response. If the reader’s interest has been aroused, many current books, articles, and reviews, and growing numbers of educational internet sites, including the one that supports this textbook (see the preface), are available to flesh out the details on the scaffolding provided by this book.
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2 CELLS AND TISSUES OF THE IMMUNE SYSTEM
INTRODUCTION
The immune system includes a wide variety of cells that function independently and in concert with one another. Chapter 1 introduced the major immune cells derived from lymphoid or myeloid progenitor cells in the bone marrow. In this chapter, we will further define the functional and phenotypic