Created by CK-12 Foundation/Adapted by Christine Miller
Case Study: Defending Your Defenses
Twenty-six-year-old Hakeem 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 17.1.1, he noticed an unusual lump.
Hakeem 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, although he is concerned about Hakeem’s lack of appetite and weight loss. All of those symptoms combined can indicate a type of cancer called lymphoma. An infection, however, is a more likely cause, particularly in a young person like Hakeem. Dr. Hayes prescribes an antibiotic in case Hakeem 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.
Hakeem 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. This helps to determine whether the tissue contains cancerous cells.
The initial results of the biopsy indicate that Hakeem 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’s lymphoma and non-Hodgkin’s lymphoma. Non-Hodgkin lymphoma (NHL), in turn, has many subtypes. The subtype depends on several factors, including which cell types are affected. Some subtypes of NHL, for example, affect immune system cells called B cells, while others affect different immune system cells called T cells.
Dr. Hayes explains to Hakeem that it is important to determine which type of lymphoma he has, in order to choose the best course of treatment. Hakeem’s biopsied tissue will be further examined and tested to see which cell types are affected, as well as which specific cell-surface proteins — called antigens — are present. This should help identify 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 Hakeem 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.
In this chapter, you will learn about the — 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 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 and , called the neuroimmune system.
- The organs, cells, and responses of the innate immune system, which includes physical barriers (such as and ), chemical and biological barriers, inflammation, activation of the complement system of molecules, and non-specific cellular responses (such as ).
- 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 .
- 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:
- What are the functions of lymph nodes?
- What are B and T cells? How do they relate to lymph nodes?
- What are cell-surface antigens? How do they relate to the immune system and to cancer?
Mayo Clinic Staff. (n.d.). Hodgkin’s lymphoma [online article]. MayoClinic.org. https://www.mayoclinic.org/diseases-conditions/hodgkins-lymphoma/symptoms-causes/syc-20352646
Mayo Clinic Staff. (n.d.). Non-Hodgkin’s lymphoma [online article]. MayoClinic.org. https://www.mayoclinic.org/diseases-conditions/non-hodgkins-lymphoma/symptoms-causes/syc-20375680
The body system in humans and other animals that protects the organism by distinguishing foreign tissue and neutralizing potentially pathogenic organisms or substances.
A microorganism which causes disease.
The central nervous system organ inside the skull that is the control center of the nervous system.
A thin, tubular bundle of central nervous system tissue that extends from the brainstem down the back to the pelvis and connects the brain with the peripheral nervous system.
The major organ of the integumentary system that covers and protects the body and helps maintain homeostasis, for example, by regulating body temperature.
A slimy substance produced by mucous membranes that traps pathogens, particles, and debris.
The process by which a cell uses its plasma membrane to engulf a large particle, giving rise to an internal compartment called the phagosome.
An antibody, also known as an immunoglobulin, is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as pathogenic bacteria and viruses.