A lucid, up-to-date account of the body's immune system from a pro who has taught the subject at UCLA for 25 years.

Infectious disease is news Big Time these days - it has been ever since AIDS appeared. What is fascinating is the game of catch-up that science has been playing - unraveling the intricacies of the body's immune system and, more recently, its intimate relation to the nervous system. Clark reminds us that just a generation ago the body's defenses were thought to consist of only antibodies: the molecules that destroy foreign invaders. Not only does Clark explain how the body can be stimulated by vaccines, to make millions of antibodies, but he goes into detail about T cells - the other arm of the immune system. T cells (the T is for thymus, where they are made) come in several varieties, of which the most noted today are the "killer" T cells that search and destroy aberrant cells, and the "helper" T cells that are killed by the AIDS virus. Sometimes the immune system is overzealous, however, mounting an attack that adds insult to injury. There is a misreading of molecular markers, resulting in attacks on healthy cells as happens in autoimmune diseases such as multiple sclerosis (the war within), and sometimes there is a need to suppress the system - in the case of organ transplants. Clark's upbeat book suggests that we can curb excesses, as well as stimulate a weakened response with new drugs or gene therapy approaches. He is convinced that ongoing discoveries of the brain-immune system dialog will lead to new approaches to therapy. He is also aware of the pressing need for organ transplants, raising provocative ethical issues but at the same time providing a valid Uniform Anatomical Gift Act donor card for readers to fill out.

A good idea, given that his overall enthusiasm and mastery in explaining complex science might just persuade more than a few readers.

The human immune system is a chemical symphony of astounding complexity; an armed sentry on never-ending patrol; a circulating brain that remembers every enemy. Since ancient times, physicians have tried to manipulate these powerful attributes through vaccines and other attempts to thwart disease.

Not until 20th-century science brought an arsenal of biotechnologies to the mission have scientists really begun to appreciate the role of circulating immune agents - such as antibodies and cells that rush to clear debris and bacteria from a cut, wage a life-long war against pollen, or do battle with a tumor. , Almost daily, fresh insights on the human immune system are prompting new strategies against diseases such as AIDS and cancer, seeming to offer us cause for cheering.

But as UCLA immunologist William R. Clark notes in At War Within, we face a paradox. The human immune system, Clark observes, evolved primarily to keep us alive through our prime breeding years. But we now live decades beyond those years. So, he writes, "we have increasingly become the victims of the cumulative effects of the lethal efficiency - and sometimes bumbling overzealousness - of our own immune systems. That's why we suffer the biological self-hatred of autoimmune diseases such as rheumatoid arthritis or multiple sclerosis.

Or we suffer ironies: The virus that causes hepatitis B, one of the world's worst infectious killers, is not directly lethal to human liver cells. Rather, it prompts such an aggressive and unceasing attack from an infected person's own immune cells that they eventually destroy the liver.

There's a superficial tone and wide scope to At War Within. It's not surprising to learn that Clark has taught immunology for 25 years - each chapter has the feel of an introductory course's lecture notes, smoothed and clarified in a good editor's word processor. There are no startling new findings here, and few particularly provocative ideas. But Clark's historical background and clear explanations of these microscopic processes offers the kind of primer that lay readers will find valuable.

While we noisily stumble through our daily lives trying (with greater or less success) to negotiate the world, our immune systems handle our microscopic adventures with the same outside forces silently and efficiently. Unrecognized until the last century, the immune system is acknowledged to be the single major determinant of health and disease. Its task is to ask one profound question: what is self, and what is non-self? Its fantastically elegant, versatile and vigilant organization scans virtually every molecule we come in contact with. When the system is working, microbial barbarians at the door are handily dispatched. When it is not, the consequences for us are dire.

In "At War Within: The Double-edged Sword of Immunity," William R. Clark, who teaches immunology at the University of California, Los Angeles, gives us a summary of his rapidly developing field. Starting with a brief scientific history, he goes on to explain the rudiments of the immune system and the terrible consequences that can occur when the immune system is absent, as with AIDS, or when it is misguided, as with autoimmune diseases like lupus. He delves into the ethical questions that have arisen now that we can trick the immune system into accepting alien tissues in organ transplantation. And there is a tantalizing section on the new discipline of psychoneuroimmunology - the relation of the mind to the immune system. That all of this is covered in 276 pages is a telling indication of the books strengths and its weakness. As a panoramic overview, it's highly readable and interesting, but by necessity it lacks depth. It is equally illuminating and frustrating.

Perhaps the most significant omission is a vivid, close-up portrait of the immune system itself. This is a real loss, because one would have to look long and hard throughout the scientific and medical world to find a cast of characters as strange and brilliant as those of the immune system. As a case in point, macrophages (the word derives from the Greek for "big eater") versatile and ubiquitous in the immune system, are described in these pages as gourmand housekeepers from hell: "They are basically the vacuum cleaners and filter feeders of the immune system. They ingest and digest (and often regurgitate) everything in sight that is not part of a normal healthy tissue." In reality, the macrophage is a highly mobile cell that can move nimbly through virtually any tissue on its delicate, foot-like pseudopods. It takes up residence in lymph nodes, combing through the microscopic flotsam and jetsam and sending out an alarm if any worrisome invader is detected. The macrophage has an enormous molecular vocabulary of signals to other cells - nearly a hundred discrete messages directing immunological responses. It can even structurally transform itself, when dealing with especially resistant microbes, into a giant megacell.

Mr. Clark's strong suit is explaining theoretical issues - in particular the relation of the immune system to the brain. He makes a convincing parallel between these two systems, noting that they are the only parts of the organism with the capacity for the identification and memory of encounters with the outside world. They both can learn, and they both have difficulty unlearning. (Any psychiatrist will vouch for this phenomenon of mental intransigence.) Each of them has a language for cell-cell communication. As Mr. Clark puts it, "It is almost as if the immune system were a chemical extension of the brain, floating around in the bloodstream."

Amazingly, recent research has begun to demonstrate that the two systems talk to each other. "It turns out," Mr. Clark says, "that the mind and the body are completely fluent both in their own language and in the language of the other." Science is closing in on the molecular basis for a fact that has been intuited since time immemorial: emotional conflict undermines physical health, and absence of stress promotes it. This nearly invisible cellular system, laced intricately throughout the organism, is a crucial link between body and mind.

In the end, Mr. Clark sees the mind and the immune system as a nearly unbeatable duo. "If the built-in defensive genes we have cannot save us," he writes, ""we may find that what saves us is the application of our own intelligence and accumulated cultural wisdom. There is precious little a virus - even one as deadly as HIV - can do about that." It is a surprisingly sunny view for the 1990s. But is it true? Mr. Clark is slighting one key fact: nature, ever ingenious at insuring its own survival, is on the side of the microbes too.

Today the news informs us that our collective health is under attack. Tuberculosis is on the resurgence, AIDS continues its onslaught, and allergies plague many people. Clark, who teaches immunology at UCLA, unites these subjects and others in a lucid discussion of our body's immune system. Devoting each chapter to a unique malady or condition, he provides the details needed to understand our immune structure, particularly when it unravels and turns on itself These details do not overwhelm the general reader's grasp of the topic; instead, they support it. Clark's presentation is straightforward, arranged well, and includes historical background. Highly recommended for all collections.

A new genre: immunology for poets! Clark is an experienced researcher and teacher, and it shows. He communicates well and knows his subject; poets will have a good read. Many people have problems with their immune systems, so the reading may be practical. As the subtitle indicates, the topics include various autoimmune problems and organ transplantation. Other chapters treat AIDS (the best 35 pages this reviewer has ever read on the topic); the ethics of organ transplantation; mind-immune system interactions; and immune deficiency diseases, among other topics. There is an Appendix on immunological tolerance. Clark has included quite a bit of history, with enough personal glimpses into the lives of individual researchers and the research community in general to add to the readability of the book. There are only a handful of diagrams or tables. There is a short index, and a short bibliography - too short; it does not cover many of the sources mentioned. The book could serve as good supplementary reading and should be in all libraries. Even professional immunologists will learn something.