In the seventeenth century, smallpox reigned as England's worst killer. Luck, more than anything else, decided who would live and who would die. That is, until Lady Mary Wortley Montagu, an English aristocrat, moved to Constantinople and noticed the Turkish practice of "ingrafting," or inoculation, which, she wrote, made "the smallpox…entirely harmless." Convinced by what she witnessed, she allowed her six-year-old son to be ingrafted, and the treatment was a complete success - the young Montagu enjoyed lifelong immunity from smallpox. Unfortunately for England, Lady Montagu's "discovery" would remain a quiet one; it would be almost 150 years before inoculation (in the more modern form of vaccination) would become widely accepted in the West while the medical community struggled to understand the way our bodies defend themselves against disease.

William Clark's At War Within takes us on a fascinating tour through the immune system, examining the history of its discovery, the ways in which it protects us, and how it may bring its full force to bear at the wrong time or in the wrong place. Scientists have only recently come to realize that this elegant defense system not only has the potential to help, as in the case of smallpox, but also the potential to do profound harm in problems ranging from allergies to AIDS, and from organ transplants to cancer. Dr. Clark describes the myriad of medical problems involving the immune system, and he systematically explains each one. For example, in both tuberculosis and AIDS, the underlying pathogens take up residence inside the immune system itself, something Clark compares to a prowler taking up residence in your house, crawling about through the walls and ceilings while waiting to do you in. He discusses organ transplants, showing how the immune system can work far too well, and touching on the heated ethical debate over the use of both primate and human organs. He explores the mind's powerful ability to influence the performance of the immune system; and the speculation that women, because they have developed more powerful immune systems in connection with childbearing, are more prone than men to contracting certain autoimmune disorders such as lupus. Clark explains how the disease originated, and the ways in which it operates. And, in each section, we learn about the most recent medical breakthroughs.

At first glance, it may appear that our immune system faces daunting odds; it must learn to successfully fend off not thousands, but millions, of different types of microbes. Fortunately, according to Clark, it would be almost impossible to imagine a more elegant strategy for our protection than the one devised by our immune systems. At War Within provides a thorough and engaging explanation of this most complex and delicately balanced of mechanisms.

From At War Within

The immune system can and does provide a powerful defense against potential pathogens, but what is perhaps less obvious is that it is also capable of bringing too much power to bear during the course of clearing away foreign invaders. Like an army lashing out blindly against an unseen and unmeasured enemy, the immune system is capable of using excessive deadly force in the wrong time or place - it is capable of overkill. And as almost always happens in such cases, the most devastating damage of all may be done to innocent bystanders. The result could be nothing more than a mildly annoying allergy. But it can be more deadly. People may die from hepatitis, not because the virus destroys the liver - the virus itself is quite harmeless - but because of the violence of the attack of the immune system on the infected liver….Our immune systems are thus like a high-wire balancing act. Death lies on either side. Science and medicine have given us the means to keep our balance for most of the length of the wire, but it is still a very risky act.