The immune system is responsible for protecting the body against bacteria, viruses, fungi, toxins, parasites, and cancer. It works with the organs of the lymphatic system, the thymus, spleen, and lymph nodes, to clear the body of these disease-causing agents.

Outline

• The Lymphatic System
• Defenses Against Disease
• Antibodies
• Immune Responses and Acquired Immunities
• Major Immune System Disorders

Learning Outcomes

After completing Chapter 32, you will be able to:

 32.1 List the pathways and organs of the lymphatic system and give their locations.
 32.2 Define lymph and tell how it is circulated in the body.
 32.3 Define the terms infection, pathogen, and antigen.
 32.4 List and describe the nonspecific body defense mechanisms.
 32.5 Explain the signs and causes of inflammation.
 32.6 Explain what is meant by specific body defenses.
 32.7 Define B cells and T cells and describe their locations and functions.
 32.8 Explain the importance of MHC proteins.
 32.9 List the different types of T cells and describe their functions.
 32.10 Explain how antibodies fight infection.
 32.11 List the different types of antibodies and tell how they differ.
 32.12 Define complement proteins and give their function.
 32.13 Explain the difference between the primary immune response and secondary immune response.
 32.14 Explain the four different types of acquired immunities.
 32.15 Describe the function of a vaccine.
 32.16 Define the terms cancer and carcinogen.
 32.17 Describe how cancers are diagnosed and treated.
 32.18 Explain how cancers are classified.
 32.19 Describe how allergies develop.
 32.20 Describe the causes, signs and symptoms, and treatments of other common immune disorders.

Summary

The body's major line of defense is the immune system. The primary function of the immune system is to protect the body against infection, toxins, and cancer. Its major organs include the spleen, thymus, and lymph nodes. The lymph vessels transport the immune fluid, called lymph, throughout the body. The two major lymphatic collecting ducts are the thoracic duct and the right lymphatic duct.

The defenses of the immune system can be either nonspecific or specific. Lymphocytes are the major types of cells in the immune system and are classified as either B cells or T cells. When the body is first exposed to an antigen, a primary immune response occurs. This response is less specific and slower than a secondary immune response, which occurs the next time the body is exposed to the same antigen.