Immunity and Diseases of the Immune System

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Questions and Answers

What is the primary function of the immune system?

To mediate the digestion of food

To defend the body against pathogenic microbes (correct)

To produce cancer cells

To regulate body temperature

Which type of immunity is mediated by cells and proteins that are always present and act immediately against any infection?

Humoral immunity

Innate immunity (correct)

Cell-mediated immunity

Adaptive immunity

What is the primary function of natural killer cells?

To produce antibodies

To phagocytose foreign particles

To activate phagocytes to kill ingested microbes

To recognize and eliminate infected cells (correct)

Which type of adaptive immunity is mediated by soluble antibody proteins?

Humoral immunity Signup and view all the answers

What is the primary function of T lymphocytes in cell-mediated immunity?

To directly kill infected cells Signup and view all the answers

What is the term for the proteins produced by helper T cells that activate phagocytes to kill ingested microbes?

Cytokines Signup and view all the answers

What is the primary function of the epithelial barriers in innate immunity?

To prevent microbe entry Signup and view all the answers

What is the term for the collection of cells and molecules that are responsible for defending our body against pathogenic microbes?

Immune system Signup and view all the answers

What is the primary function of antigen-presenting cells?

To capture microbial antigens and display them to lymphocytes Signup and view all the answers

What type of dendritic cells occur as two functionally distinct types?

Interdigitating DCs and Follicular dendritic cells Signup and view all the answers

What is the primary cause of systemic anaphylactic reactions?

Injected allergens Signup and view all the answers

What is the role of macrophages in cell-mediated immunity?

To ingest microbes and display them for recognition by T lymphocytes Signup and view all the answers

What is a common symptom of systemic anaphylactic reactions?

Gastrointestinal cramps Signup and view all the answers

What is the function of T lymphocytes in the adaptive immune response?

To secrete cytokines that recruit and activate other leukocytes Signup and view all the answers

What is the term used to imply a hereditary predisposition to localized atopic disorders?

Atopy Signup and view all the answers

What is the primary mechanism of type II, antibody-mediated cytotoxic disorders?

Antibody-dependent cell-mediated cytotoxicity Signup and view all the answers

What is the role of lymphoid tissues in the immune response?

To divide into generative and peripheral organs for immune responses Signup and view all the answers

What is hypersensitivity defined as?

An exaggerated immune response to a foreign agent resulting in injury to the host Signup and view all the answers

What is the primary function of T lymphocytes in the immune system?

To provide important stimuli for antibody responses to protein antigens Signup and view all the answers

What is the result of the formation of insoluble antigen-antibody complexes in type III, immune-complex disorders?

Activation of complement system Signup and view all the answers

Which of the following is an example of a type II, antibody-mediated cytotoxic disorder?

Mismatched blood transfusion Signup and view all the answers

Which type of immune cells are responsible for recognizing molecules expressed on stressed or infected cells?

Natural Killer cells Signup and view all the answers

What is an allergen?

A foreign substance capable of inducing an immune response Signup and view all the answers

What is the primary characteristic of localized atopic disorders?

Genetic predisposition Signup and view all the answers

What is the primary function of B lymphocytes in the immune system?

To synthesize antibodies or immunoglobulins Signup and view all the answers

What is the result of an inappropriate activation of the immune system?

Debilitating or life-threatening illnesses, such as allergic or hypersensitivity reactions Signup and view all the answers

What is the primary mechanism of systemic anaphylactic reactions?

IgE-mediated response Signup and view all the answers

Which of the following is NOT a characteristic of T lymphocytes?

They detect free or circulating antigens Signup and view all the answers

What is the function of inhibitory receptors expressed on Natural Killer cells?

To avoid attacking normal host cells Signup and view all the answers

What happens to the expression of class I MHC molecules on infected cells?

They are downregulated Signup and view all the answers

What is the outcome of the reaction of the cells of innate and adaptive immunity?

Inflammation, which is a beneficial process Signup and view all the answers

How do B cells respond to stimulation?

They differentiate into plasma cells that secrete large amounts of antibodies Signup and view all the answers

What is the primary function of macrophages that are activated during a delayed hypersensitivity response?

To function as phagocytic and antigen-presenting cells Signup and view all the answers

Which type of antigens induces cell-mediated immunity with a pronounced macrophage response?

Particulate antigens that are large, insoluble, and difficult to eliminate Signup and view all the answers

What is the term for the microscopic aggregation of epithelioid cells surrounded by a layer of lymphocytes?

Granuloma Signup and view all the answers

What is the primary role of cytokines in the delayed hypersensitivity response?

To attract T or B lymphocytes, as well as monocytes, neutrophils, eosinophils, and basophils Signup and view all the answers

What is the term for inflammation characterized by the formation of granulomas?

Granulomatous inflammation Signup and view all the answers

What is the primary mechanism of direct T-cell–mediated cytotoxicity?

Direct killing of antigen-bearing cells Signup and view all the answers

What is the common factor between Hashimoto's thyroiditis and graft-versus-host transplant rejection?

Involvement of direct T-cell–mediated cytotoxicity Signup and view all the answers

What is the term for the reaction to the tuberculin test, which involves redness and induration of the skin?

Delayed hypersensitivity response Signup and view all the answers

Study Notes

Immunity and Immune System

Immunity is protection against infections, and the immune system is the collection of cells and molecules responsible for defending the body against pathogenic microbes, preventing cancer cell proliferation, and mediating tissue healing.
Defense against microbes consists of two types of reactions: innate immunity (natural or native immunity) and adaptive immunity (acquired or specific immunity).

Innate Immunity

Mediated by cells and proteins that are always present and act immediately against infection.
Major components of innate immunity include:
- Epithelial barriers (skin, gastrointestinal tract, and respiratory tract) that prevent microbe entry.
- Phagocytic leukocytes (neutrophils and macrophages).
- Natural killer (NK) cells.
- Circulating plasma proteins, including the complement system.

Adaptive Immunity

Normally silent, responding to the presence of infectious microbes by becoming active and neutralizing/eliminating them.
Components of adaptive immunity include:
- Lymphocytes (B cells and T cells) and their products.
- Humoral immunity: mediated by soluble antibody proteins produced by B lymphocytes (B cells).
- Cell-mediated (or cellular) immunity: mediated by T lymphocytes (T cells) important in defense against intracellular microbes.

Cells and Tissues of the Immune System

Lymphocytes: mediators of adaptive immunity.
Specialized antigen-presenting cells (APCs): capture and display microbial and other antigens to lymphocytes.
Effector cells: eliminate antigens (microbes).

Lymphocytes

Present in circulation and in lymphoid organs as two types:
- T lymphocytes (mature in the thymus).
- B lymphocytes (mature in the bone marrow).
T Lymphocytes:
- Effector cells of cellular immunity.
- Provide stimuli for antibody responses to protein antigens.
- Recognize protein antigens displayed on other cells bound to MHC proteins.
B Lymphocytes:
- Synthesize antibodies or immunoglobulins (five classes: IgG, IgM, IgA, IgE, and IgD).
- Differentiate into plasma cells, which secrete large amounts of antibodies, mediators of humoral immunity.

Natural Killer Cells

Lymphocytes of innate immunity with limited set of activating receptors.
Recognize molecules expressed on stressed or infected cells or cells with DNA damage, then kill these cells.
Express inhibitory receptors that recognize self-class I MHC molecules, avoiding attack on normal host cells.

Antigen-Presenting Cells

Specialized cells that capture microbial antigens and display them to lymphocytes.
Include dendritic cells (DCs) and macrophages.
Dendritic cells: cells with fine dendritic cytoplasmic processes, occurring as two functionally distinct types (interdigitating DCs and follicular DCs).
Macrophages: ingest microbes and display them for recognition by T lymphocytes, which activate macrophages to kill the microbes.

Effector Cells

Include:
- Natural killer cells.
- Antibody-secreting plasma cells.
- T lymphocytes.
- Macrophages.
T lymphocytes secrete cytokines, recruiting and activating other leukocytes, such as neutrophils and eosinophils, which function in defense against pathogens.

Lymphoid Tissues

Divided into:
- Generative (primary) organs, where lymphocytes express antigen receptors and mature (thymus and bone marrow).
- Peripheral (secondary) lymphoid organs, where adaptive immune responses develop (lymph nodes, spleen, and mucosal and cutaneous lymphoid tissues).

Immune Response Disorders

Allergic or hypersensitivity reactions:
- Result from exaggerated immune responses to environmental antigens, causing inflammation and tissue injury.
- Examples: systemic anaphylactic reactions, localized atopic disorders, and type II, III, and IV hypersensitivity reactions.

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Description

Learn about the immune system, its functions, and the defense against microbes through innate and adaptive immunity. Understand the role of immunity in preventing infections and cancer.