ABSTRACT
Study objectives Describe the functions and activities of the immune system List the symptoms of inammation Explain the steps of the inammatory response and how they protect against bacterial invasion Explain how interferon defends against invading viruses and tumor cells Describe the function of natural killer (NK) cells Describe how the complement system defends against invading bacteria Compare and contrast the general characteristics of the innate immune system and the adaptive immune system List the different types of antibodies and their functions Describe the two functional regions of the antibody molecule Explain how antibodies defend against invading bacteria Explain the clonal selection theory Compare and contrast primary responses and secondary responses Distinguish between active immunity and passive immunity List the three types of T cells and their functions Explain how cytotoxic T cells defend against invading viruses Distinguish between class I major histocompatibility complex (MHC) glycoproteins and class II MHC glycoproteins
8. Introduction Immunity is dened as the body’s ability to eliminate foreign organisms or substances as well as abnormal cells. The immune system consists of tissues, cells, and molecules that work together to form an internal defense system. As such, it is capable of recognizing and then destroying or neutralizing organisms and substances that are foreign to the “normal self.” The immune system performs several functions and activities that are important in maintaining health or causing disease:
Defense against infection Removal of cells and tissue debris Immune surveillance Allergies and autoimmune diseases Rejection of tissue grafts and newly introduced proteins
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The immune system provides defense against infection by pathogenic microorganisms such as bacteria, viruses, fungi, and parasites. Immune deciency results in an increased susceptibility to infections. This is exemplied by patients with AIDS or those receiving chemotherapy or taking immunosuppressant drugs.
