Book excerpt: Immunology, or the study of the immune system, is an IMMUNOLOGY extremely relevant area of research in medicine and biology. The immune system provides many barriers against infection. Diseases including autoimmunity, allergies, and cancer may develop when the immune system isn’t working properly. Immune responses are also being linked to the onset of numerous cardiovascular, metabolic, and neurodegenerative diseases like Alzheimer’s, which were previously thought to have no immunologic basis. From the eighteenth-century work of Edward Jenner, which led to the modern vaccination (likely saving more lives than any other medical advance), to many scientific breakthroughs in the 19th and 20th centuries, which led to, among other things, the identification of blood groups, safe organ transplantation, and now ubiquitous use of monoclonal antibodies in science & healthcare, immunology has played a crucial role in advancing medical and scientific knowledge and practice. Research in immunotherapy, autoimmune illnesses, and vaccines for new infections like Ebola continues to broaden our knowledge of how to address major health problems. The development of novel diagnostics and therapies for the management of a broad variety of illnesses has been aided by our increased knowledge of fundamental immunology, which is crucial for clinical as well as commercial use. Flow cytometry and antibody technology are two examples of cutting-edge research tools made possible by the intersection of immunology and the advancement of technology.