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Biology LibreTexts

20.1: Case Study: Your Defense System

  • Page ID
    22595
  • Case Study: Defending Your Defenses

    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, like the doctor is doing in Figure \(\PageIndex{1}\), he noticed an unusual lump.

    doctor palpating lymph nodes under jaw.
    Figure \(\PageIndex{1}\): (NIH, public domain; via wikimedia.org; NIH).

    Brian went to his doctor who performed a physical exam and determined that the lump was a swollen lymph node. Lymph nodes are part of the immune system, and they will often become enlarged when the body is fighting off an infection. Dr. Hayes thinks that the swollen lymph node and fatigue could be signs of a viral or bacterial infection, or indicate a type of cancer called lymphoma. However, an infection is a more likely cause, particularly in a young person like Brian. Dr. Hayes prescribes an antibiotic in case Brian has a bacterial infection and advises him to return in a few weeks if his lymph node does not shrink or if he is not feeling better.

    Brian returns a few weeks later. He is not feeling better and his lymph node is still enlarged. Dr. Hayes is concerned and orders a biopsy of the enlarged lymph node. A lymph node biopsy for suspected lymphoma often involves the surgical removal of all or part of a lymph node, to determine whether the tissue contains cancerous cells.

    The initial results of the biopsy indicate that Brian does have lymphoma. Although lymphoma is more common in older people, young adults and even children can get this disease. There are many types of lymphoma, with the two main types being Hodgkin and non-Hodgkin lymphoma. Non-Hodgkin lymphoma (NHL), in turn, has many subtypes depending on factors such as which cell types are affected. For instance, some subtypes of NHL affect immune system cells called B cells, while others affect different immune system cells called T cells.

    Dr. Hayes explains to Brian that it is important to determine which type of lymphoma he has, in order to choose the best course of treatment. Brian’s biopsied tissue will be further examined and tested to see which cell types are affected and which specific cell-surface proteins, called antigens, are present. This should help in identifying his specific type of lymphoma.

    As you read this chapter, you will learn about the functions of the immune system, and the specific roles that its cells and organs — such as B and T cells and lymph nodes — play in defending the body. At the end of this chapter, you will learn what type of lymphoma Brian has and what some of his treatment options are, including treatments that make use of the biochemistry of the immune system to fight cancer with the immune system itself.

    Chapter Overview: Immune System

    In this chapter, you will learn about the immune system — the system that defends the body against infections and other causes of disease such as cancerous cells. Specifically, you will learn about:

    • How the immune system identifies normal cells of the body as “self” and pathogens and damaged cells as “non-self.”
    • The two major subsystems of the general immune system: the innate immune system which provides a quick but non-specific response; and the adaptive immune system which is slower but provides a specific response that often results in long-lasting immunity.
    • The specialized immune system that protects the brain and spinal cord called the neuroimmune system.
    • The organs, cells, and responses of the innate immune system which includes physical barriers such as skin and mucus; chemical and biological barriers; inflammation; activation of the complement system of molecules; and non-specific cellular responses such as phagocytosis.
    • The lymphatic system — which includes white blood cells called lymphocytes, lymphatic vessels which transport a fluid called lymph, and organs such as the spleen, tonsils, and lymph nodes —and its important role in the adaptive immune system.
    • Specific cells of the immune system and their functions, including B cells, T cells, plasma cells, and natural killer cells.
    • How the adaptive immune system can generate specific and often long-lasting immunity against pathogens through the production of antibodies.
    • How vaccines work to generate immunity.
    • How cells in the immune system detect and kill cancerous cells.
    • Some strategies that pathogens employ to evade the immune system.
    • Disorders of the immune system including allergies, autoimmune diseases (such as diabetes and multiple sclerosis), and immunodeficiency resulting from conditions such as HIV infection.

    As you read the chapter, think about the following questions:

    1. What are the functions of lymph nodes?

    2. What are B and T cells and how do they relate to lymph nodes?

    3. What are cell-surface antigens? How do they relate to the immune system and to cancer?