Porth's Pathophysiology, 9e

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Innate and Adaptive Immunity THE IMMUNE RESPONSE Cytokines and Their Role in Immunity General Properties of Cytokines Chemokines Colony-Stimulating Factors INNATE IMMUNITY Epithelial Barriers Cells of Innate Immunity Neutrophils and Macrophages Dendritic Cells Natural Killer Cells and Intraepithelial Lymphocytes Pathogen Recognition

Nancy A. Moriber

The human body is constantly exposed to potentially ­deleterious microorganisms and foreign substances. Therefore, it has evolved a complete system composed of complemen- tary and interrelated mechanisms to defend against invasion by bacteria, viruses, and other foreign substances. Through recognition of molecular patterns, the body’s immune system can distinguish itself from these foreign substances and can discriminate potentially harmful from nonharmful agents. In addition, it can defend against abnormal cells and molecules that periodically develop. The skin and its epithelial layers in conjunction with the body’s normal inflammatory processes make up the first line of the body’s defense and confer innate or natural immunity to the host. Once these protective bar- riers have been crossed, the body relies upon a second line of defense known as the adaptive immune response to eradi- cate infection by invading organisms. The adaptive immune response develops slowly over time but results in the develop- ment of antibodies capable of targeting specific microorgan- isms and foreign substances should a second exposure occur. This chapter covers immunity and the immune system, including a complete discussion of innate and adaptive immu- nity. Concepts related to key cellular function, recognition systems, and effector responses integral to the immune system are also presented. In addition, developmental aspects of the immune system are discussed.

Pattern Recognition Toll-Like Receptors Soluble Mediators of Innate Immunity Opsonins Inflammatory Cytokines Acute-Phase Proteins The Complement System ADAPTIVE IMMUNITY Antigens Cells of Adaptive Immunity Lymphocytes

Major Histocompatibility Complex Molecules Antigen-Presenting Cells B Lymphocytes and Humoral Immunity Immunoglobulins Humoral Immunity T Lymphocytes and Cellular Immunity Helper T Cells and Cytokines in Adaptive Immunity Lymphoid Organs Thymus Lymph Nodes Spleen Other Secondary Lymphoid Tissues Active versus Passive Immunity Regulation of the Adaptive Immune Response DEVELOPMENTAL ASPECTS OF THE IMMUNE SYSTEM Transfer of Immunity from Mother to Infant Immune Response in the Older Adult Regulatory T Cells Cytotoxic T Cells Cell-Mediated Immunity

THE IMMUNE RESPONSE

After completing this section of the chapter, you should be able to meet the following objectives: •• Discuss the function of the immune system. •• Contrast and compare the general properties of innate and adaptive immunity. •• Characterize the chemical mediators that orchestrate the immune response.

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