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Biology LibreTexts

20: Immune System

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  • This chapter outlines the layered responses of the human immune system, including both innate and adaptive immune responses. It also describes the structures and functions of the lymphatic system, with a focus on its roles in host defense. In addition, the chapter examines three different types of immune system disorders.

    • 20.1: Case Study: Your Defense System
      Twenty-six-year-old Brian wasn’t feeling well. He was more tired than usual, dragging through his workdays despite going to bed earlier, and napping on the weekends. He didn’t have much of an appetite and had started losing weight. When he pressed on the side of his neck, he noticed an unusual lump.
    • 20.2: Introduction to the Immune System
      The immune system is a host defense system. It comprises many biological structures —ranging from individual white blood cells to entire organs — as well as many complex biological processes. The function of the immune system is to protect the host from pathogens and other causes of disease such as tumor cells. To function properly, the immune system must be able to detect a wide variety of pathogens.
    • 20.3: Lymphatic System
      The lymphatic system is a collection of organs involved in the production, maturation, and harboring of white blood cells called lymphocytes. It also includes a network of vessels that transport or filter the fluid known as lymph in which lymphocytes circulate. The figure below shows major lymphatic vessels and other structures that make up the lymphatic system.
    • 20.4: Innate Immune System
      The innate immune system is a subset of the human immune system that produces rapid but non-specific responses to pathogens. Innate responses are generic rather than tailored to a particular pathogen. Every pathogen that is encountered is responded to in the same general ways by the innate system. Although the innate immune system provides immediate and rapid defenses against pathogens, it does not confer long-lasting immunity to them.
    • 20.5: Adaptive Immune System
      The adaptive immune system is a subsystem of the overall immune system. It is composed of highly specialized cells and processes that eliminate specific pathogens and tumor cells. An adaptive immune response is set in motion by antigens that the immune system recognizes as foreign. Unlike an innate immune response, an adaptive immune response is highly specific to a particular pathogen (or its antigen).
    • 20.6: Disorders of the Immune System
      An allergy is a disorder in which the immune system makes an inflammatory response to a harmless antigen. Any antigen that causes allergies is called an allergen. Common allergens include pollen, dust mites, mold, specific foods such as peanuts, insect stings, and certain medications such as aspirin. Autoimmune diseases occur when the immune system fails to recognize the body’s own molecules as self and attacks them, causing damage to tissues and organs.
    • 20.7: Case Study Lymphoma Conclusion and Chapter Summary
      This woman is participating in a bike ride to raise funds for leukemia and lymphoma research. Leukemia and lymphoma are blood cancers. About every three minutes, one person in the U.S. is diagnosed with blood cancer. Lymphoma is the most common type of blood cancer. As a lymphoma patient, Brian, who you learned about in the beginning of this chapter, may eventually benefit from research funded by a bike ride like this one. In this chapter you learned about the immune system.

    Thumbnail: From left to right: erythrocyte ,platelet and lymphocyte. Image used with permission (Public Domain; The National Cancer Institute at Frederick ).​​​