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
- 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 Wei 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.
- 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: Human Microbiome
- The scientific evidence supporting the gut microbiome in relation to health maintenance and links with various disease states afflicting humans, from metabolic to mental health, has grown dramatically in the last few years. Strategies addressing the positive modulation of microbiome functionality associated with these disorders offer huge potential to the food and pharmaceutical industries to innovate and provide therapeutic solutions to many of the health issues affecting modern society.
- 20.8: Case Study Conclusion: Lymphoma and Chapter Summary
- About every three minutes, one person in the U.S. is diagnosed with blood cancer, the most common type of which is lymphoma. Wei, who was diagnosed with lymphoma in the beginning of this chapter, has a difficult road ahead, but he and his medical team are optimistic that he may be able to be cured. More research into how the immune system functions may lead to even better treatments for lymphoma, and other types of cancers, in the future.
Thumbnail: From left to right: erythrocyte, platelet, and lymphocyte. (Public Domain; The National Cancer Institute at Frederick ).