• Gives a succinct account of the evolution of innate and adaptive immunity, and how they operate, primarily in humans but also drawing on examples in other animals
• Considers the consequences of too little immunity (immunodeficiency), caused for example by HIV/AIDS, and too much, leading to autoimmune and allergic diseases
• Discusses some of the important recent advances in harnessing the immune system for immunotherapies, for example in the treatment of cancers

   
The immune system is central to human health and the focus of much medical research. Growing understanding of the immune system, and especially the creation of immune memory (long lasting protection), which can be harnessed in the design of vaccines, have been major breakthroughs in medicine.
  
In this Very Short Introduction, Paul Klenerman describes the immune system, and how it works in health and disease. In particular he focuses on the human immune system, considering how it evolved, the basic rules that govern its behaviour, and the major health threats where it is important. The immune system comprises a series of organs, cells and chemical messengers which work together as a team to provide defence against infection. Klenerman discusses these components, the critical signals that trigger them and how they exert their protective effects, including so-called "innate" immune responses, which react very fast to infection, and "adaptive" immune responses, which have huge diversity and a capacity to recognise and defend against a massive array of micro-organisms. Klenerman also considers what happens when our immune systems fail to be activated effectively, leading to serious infections, problems with inherited diseases, and also HIV/AIDS. At the opposite extreme, as Klenerman shows, an over-exaggerated immune response leads to inflammatory diseases such as Multiple Sclerosis and Rheumatoid Arthritis, as well as allergy and asthma. Finally he looks at the "Immune system v2.o" — how immune therapies and vaccines can be advanced to protect us against the major diseases of the 21st century.
  
  
The Very Short Introductions Podcast: Episode 18 Immune System