Immunology (Lippincott Illustrated Reviews Series) 2nd Edition

UNIT IV

Clinical Aspects of Immunity

“To let the punishment fit the crime.”

—Sir William Gilbert, The Mikado, 1885

The immune system normally functions smoothly to protect us from the vast numbers of microbes that surround us, many of which would like nothing more than to make a meal of us. We notice those times when it stumbles, when it faces an onslaught by an intruder with which it is unfamiliar and requires some extra time to accelerate from 0 to 60. This is when we become clinically ill from infection. But far more frequently, our immune system identifies, confronts, and eliminates infectious threats without our notice.

Microbes have to be tracked to their hiding places, and they may employ their own weaponry that the immune system has to defend against. The immune system must cope with their evasive tactics. Once they have been apprehended, however, the immune system may choose from among various possible punishments. Death may be inflicted by destroying the nurseries in which microbes are reproducing. It may be inflicted by impalement or by a thousand small cuts that destroy the ability of the microbes to keep their cells intact. Sometimes microbes are poisoned, and sometimes they are forced to commit suicide. Often, they end up as a phagocyte’s meal.

No system functions perfectly all of the time—not automobiles, not computers, and not the immune system. Sometimes parts are missing or become damaged, and we are left open to increasing risk of infectious disease. On other occasions, the immune system misidentifies its targets. Instead of picking the guilty microbe out of the lineup, it mistakenly identifies its innocent neighbor and inflicts corporal punishment on its own body.

And sometimes, the immune system adopts the martial policy that “collateral damage” is unavoidable in time of war. In the hot pursuit of the microbial targets, the immune system may lay waste to innocent bystanders along the way. The pursuit may end with a shootout in which the offending microbes are killed but at the cost of a trail of extensive death or damage to normal cells and tissues.

When the immune system performs too weakly or too vigorously, medical intervention may be necessary. Missing or damaged parts can be replaced. Tonics may be administered to invigorate parts of the immune system. And through vaccination, it can be placed on red alert, poised to act with lightening speed and overwhelming force when next needed. On the other hand, an overheated immune system might need to be calmed by soothing potions. And sometimes, rogue elements need to be identified and neutralized or eliminated.

Chapter 13: The Well Patient: How Innate and Adaptive Immune Responses Maintain Health

Chapter 14: Hypersensitivity Reactions

Chapter 15: Immune Deficiency

Chapter 16: Autoimmunity

Chapter 17: Transplantation

Chapter 18: Immune Pharmacotherapy

Chapter 19: Tumor Immunity

Chapter 20: Measurement of Immune Function

Review Questions

Abbreviations

Glossary