FOREWORD

The complexity of the immune system is bewildering. Nearly one thousand genes are known today that encode specific functions in the immune system - and this does not count the millions and millions of different antibodies and T cell receptors produced from genes made by somatic rearrangements and hypermutations. The cells in which they function, lymphocytes, can exist in solitude, traveling from blood through lymphoid organs into the lymph and back. Nevertheless, a single lymphocyte needs the help of other cells in order to be created, to be selected for survival, to travel through the body, to settle in a lymphoid organ, to respond to antigen, and even to die. Cell-to-cell contacts and secreted cytokines made in the interactions between lymphocytes and their nonlymphoid environment, as well as between two or more types of lymphocytes, determine the generation and responses of cells of the immune system. All vertebrates including birds, reptiles, fish, amphibian, aquata, and mammals possess different forms of an immune system. Each of these systems learns to tolerate self-antigen and respond to foreign antigens. The immune system protects against a hostile environment of an astounding variety of viruses, bacteria, and parasites. It acquires memory for a first invasion - and we use this capacity to memorize when we vaccinate with attenuated form of the infectious agent to become immune against a second infection.

Unfortunately, many responses have pathological consequences because of allergic, inflammatory, or cytotoxic reactions against the body's own infected tissues. We inherit many different deficiencies in our immune system, or can acquire them by infection. The distinction between "self" and "nonself" antigens leading to tolerance is not always observed, can be broken, and results in autoimmune diseases that involve almost every part and organ of our body.

The composition of the immune systems is in a constant state of flux, since its cells turn over with half-lives as short as a day or as long as life. This composition is determined by genetic background, age, nutrition, interactions in inner networks, and antigenic experiences and other outer environmental influences that might go as far as psychoneuroendocrinological conditions. It is safely predictable that protocols in immunology will be vastly more numerous, more complex, and variable than those of chemistry, physics, and even molecular biology.

Is the plan too ambitious to assemble the materials and methods of a field that wide? After all, immunology uses it all - genetics, molecular biology, biochemistry, biophysics, cell biology, physiology, pathology, and preventive and therapeutic medicine. Immunology contributes to all these fields; one example, the cloning and sequencing of the first eukaryotic gene, that for l light chains, illustrates it well.

Materials and methods are the basis of an experiment that can prove or disprove an idea. They set the windows through which we observe the world, windows that define the boundaries of what we can and cannot see. They are the common grounds on which immunologists of all the different disciplines can talk to each other, reproduce each other's findings, and, in turn, expand knowledge by new experience. It is an exciting idea to think that Current Protocols in Immunology will be the sublimation of thousands and thousands of "materials and methods" sections of the endless numbers of publications of the field, a constant conference of so many different specialists.

Fritz Melchers
Basel, Switzerland