Understanding the Immune System: How it works - IMGT

Understanding the

Immune System

How It Works

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

NATIONAL INSTITUTES OF HEALTH National Institute of Allergy and Infectious Diseases National Cancer Institute

Understanding the

Immune System

How It Works

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES NATIONAL INSTITUTES OF HEALTH National Institute of Allergy and Infectious Diseases National Cancer Institute NIH Publication No. 03-5423 September 2003 niaid. nci.

Contents

1 Introduction 2 Self and Nonself 3 The Structure of the Immune System 7 Immune Cells and Their Products 19 Mounting an Immune Response 24 Immunity: Natural and Acquired 28 Disorders of the Immune System 34 Immunology and Transplants 36 Immunity and Cancer 39 The Immune System and the Nervous System 40 Frontiers in Immunology 45 Summary 47 Glossary

Introduction

Bacteria: streptococci

The immune system is a network of cells, tissues*, and organs that work together to defend the body against attacks by "foreign" invaders. These are primarily microbes (germs)--tiny, infection-causing organisms such as bacteria, viruses, parasites, and fungi. Because the human body provides an ideal environment for many microbes, they try to break in. It is the immune system's job to keep them out or, failing that, to seek out and destroy them.

Virus: herpes virus

When the immune system hits the wrong target or is crippled, however, it can unleash a torrent of diseases, including allergy, arthritis, or AIDS.

Parasite: schistosome

The immune system is amazingly complex. It can recognize and remember millions of different enemies, and it can produce secretions and cells to match up with and wipe out each one of them.

Fungus: penicillium mold

The secret to its success is an elaborate and dynamic communications network. Millions and millions of cells, organized into sets and subsets, gather like clouds of bees swarming around a hive and pass information back and forth. Once immune

*Definitions of words printed in italics are listed in the Glossary on page 47.

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