Immunology Chapter 5: Macrophages and Age Factors

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Questions and Answers

Which of the following is NOT a characteristic of exotoxins?

They activate the inflammatory response and produce fever.

They can damage the plasma membranes of host cells.

They are produced by bacteria. (correct)

They can inactivate enzymes critical to protein synthesis.

What is the primary cause of septicemia?

Viral infections.

Defects in phagocyte function.

Immune dysregulation disorders.

Proliferation of bacteria in blood. (correct)

Which of the following is NOT a characteristic of immune dysregulation disorders?

Excessive proliferation of bacteria in the bloodstream. (correct)

Secondary to mutations.

Mutations that cause excessive inflammation.

Abnormally high levels of inflammation.

How do viruses cause disease?

By interfering with host cell metabolism. Signup and view all the answers

What is a possible consequence of defects in phagocyte function?

Recurrent life-threatening infections. Signup and view all the answers

What is the role of interferon-γ (IFN-γ) in macrophage activation?

IFN-γ activates macrophages, causing them to produce proinflammatory cytokines and kill infected cells. Signup and view all the answers

Which of the following is NOT a characteristic of histamine released from mast cells?

Decreased blood flow into the affected area Signup and view all the answers

What is the primary function of memory cells in the immune system?

Memory cells differentiate into effector cells upon re-exposure to a specific antigen. Signup and view all the answers

Which of the following statements is TRUE about the T cell-dependent immune response in newborns?

The T cell-dependent immune response develops gradually during the first 6 months of life. Signup and view all the answers

Which of the following is a possible mechanism involved in Type II hypersensitivity reactions?

Opsonization and phagocytosis of target cells by macrophages. Signup and view all the answers

Which of the following is a characteristic of Type III (immune complex–mediated) hypersensitivity reactions?

They involve the formation of immune complexes that deposit in target tissues. Signup and view all the answers

Which of the following is a common impairment in the inflammatory response of neonates?

Decreased neutrophil chemotaxis Signup and view all the answers

What is the primary difference between Type I and Type II hypersensitivity reactions?

Type I reactions are mediated by IgE antibodies, while Type II reactions are mediated by IgG or IgM antibodies. Signup and view all the answers

Which immune system component is most severely affected by C3 deficiency?

Complement cascade Signup and view all the answers

What causes hyperacute graft rejection?

Preexisting antibodies Signup and view all the answers

What is a common treatment for deficient antibody production?

Gamma-globulin replacement therapy Signup and view all the answers

Which condition represents a cause of acquired immunodeficiencies?

Aging Signup and view all the answers

What type of immune deficiency is characterized by the failure of mechanisms of self-defense?

Primary immune deficiency Signup and view all the answers

Which of the following is NOT a feature of chronic graft rejection?

Immediate immune response Signup and view all the answers

What is often a factor in causing unusual infections in patients with defects in the membrane attack complex?

Bacteria of the Neisseria spp. Signup and view all the answers

Which of the following is treated by replacing host lymphocytes?

Bone marrow failure Signup and view all the answers

What primarily causes primary immune deficiencies?

Genetic defects Signup and view all the answers

Which type of immune deficiency is caused by physiological alterations or diseases?

Secondary immune deficiency Signup and view all the answers

What is the clinical hallmark of immune deficiency?

Propensity to unusual or recurrent severe infections Signup and view all the answers

Which type of infections are most common in individuals with defects in the cell-mediated immune response?

Fungal infections Signup and view all the answers

What is a defining feature of severe combined immunodeficiency?

Total lack of T-cell function and severe lack of B-cell function Signup and view all the answers

What syndrome is characterized by a complete or partial lack of the thymus?

DiGeorge syndrome Signup and view all the answers

Which of the following are NOT virulence factors produced by bacteria?

Cell wall Signup and view all the answers

What stage of infection follows the invasion or acute illness stage?

Convalescence Signup and view all the answers

What is the primary role of regulatory T lymphocytes in peripheral tolerance?

To maintain tolerance to self and beneficial foreign tissues Signup and view all the answers

Which type of hypersensitivity reaction is primarily mediated by IgE?

Type I hypersensitivity reactions Signup and view all the answers

Systemic lupus erythematosus (SLE) is characterized primarily by the production of what?

Variety of autoantibodies Signup and view all the answers

What do maternal IgG antibodies provide to the neonate during the first 6 to 10 months of life?

Provide passive immunity Signup and view all the answers

What distinguishes type III hypersensitivity reactions from other types?

They are mediated by immune complexes formed from circulating antibodies Signup and view all the answers

Which condition is an example of an alloimmune disorder?

Transfusion reactions Signup and view all the answers

Which type of hypersensitivity reaction is primarily mediated by cytotoxic T lymphocytes?

Type IV hypersensitivity Signup and view all the answers

Which of the following allergens is NOT commonly associated with allergic reactions?

Fruits Signup and view all the answers

What is the main characteristic of type IV hypersensitivity reactions?

They are mediated by T cells and do not involve antibodies Signup and view all the answers

What is a potential consequence of the decline in T-cell function in elderly individuals?

Increased susceptibility to infections Signup and view all the answers

What role do allergens play in the immune system?

They are specific antigens that trigger allergic responses Signup and view all the answers

Autoimmune diseases generally arise due to which of the following factors?

Genetic predisposition combined with an initiating event Signup and view all the answers

Heparin-induced thrombocytopenia primarily results from which mechanism?

Heparin binding leading to the formation of autoantibodies Signup and view all the answers

What type of immune response might lead to systemic reactions such as serum sickness?

Antibody-mediated hypersensitivity Signup and view all the answers

Which physiological aspect is affected in the elderly resulting in impaired humoral immunity?

Increased levels of circulating autoantibodies Signup and view all the answers

What is the result of ingesting airborne allergens?

Respiratory tract manifestations Signup and view all the answers

Study Notes

Macrophages and Interferon-γ

Macrophages are activated by interferon-γ (IFN-γ) from Th1 cells
Activated M1 macrophages secrete proinflammatory cytokines and kill infected cells in phagolysosomes

Immunologic Memory

Activated T and B cells create long-lived memory cells
Memory cells rapidly differentiate into new plasma cells or effector T cells upon re-exposure

Neonates have transiently depressed inflammatory function, particularly with neutrophil chemotaxis and alternative complement pathway activity.
Fetal/neonatal T cell-independent immune response is adequate, but T cell-dependent response develops slowly (first 6 months)
Maternal IgG antibodies cross the placenta, protecting the newborn for the first 6 months, replaced by the child's own antibodies.

Elderly persons face impaired wound healing, often due to chronic illnesses.
T-cell function declines, producing altered T cell types
Elderly individuals also experience impaired humoral immunity, with increased circulating autoantibodies.

Hypersensitivity: Allergy, Autoimmunity, and Alloimmunity

Inappropriate immune responses are exaggerated; these misdirected responses target innocuous environmental antigens (allergy), host tissues (autoimmunity), or beneficial foreign tissues (alloimmunity). Insufficient responses (immune deficiency) are also considered hypersensitivity responses
These are collectively known as hypersensitivity reactions.
Mechanisms are categorized into Type I (IgE-mediated), Type II (tissue-specific), Type III (immune complex-mediated), and Type IV (cell-mediated) reactions
Hypersensitivity reactions can be immediate (minutes to hours) or delayed (hours to days).
Allergens are antigens that provoke allergic responses.

Type I Hypersensitivity (IgE-mediated)

IgE binds to Fc receptors on mast cells
Antigen cross-linking IgE on mast cells triggers degranulation, releasing histamine (major mediator) and other inflammatory substances
Histamine, through H1 receptors, causes bronchial constriction, edema, and vasodilation. H2 receptors increase gastric acid and reduce histamine release

Type II Hypersensitivity (Tissue-Specific)

Mechanisms include complement-mediated lysis, opsonization/phagocytosis, neutrophil-mediated tissue damage, antibody-dependent cell-mediated cytotoxicity, and modulation of cellular function.

Type III Hypersensitivity (Immune Complex-Mediated)

Formation of immune complexes that deposit in tissues activates the complement cascade, attracting neutrophils.
Neutrophil release of lysosomal enzymes leads to tissue damage.
Immune complex disease can be systemic (serum sickness) or localized (Arthus reaction).

Type IV Hypersensitivity (Cell-Mediated)

Caused by cytotoxic T lymphocytes (Tc), lymphokine-producing Th1 cells, and activated macrophages.

Allergens

Common allergens include pollen, molds/fungi, foods (e.g., milk, eggs, fish, peanuts), animals, certain drugs, cigarette smoke, and house dust.

Clinical Manifestations of Allergic Reactions

Localized to areas of initial contact or intake.
Ingested allergens lead to gastrointestinal symptoms.
Airborne allergens cause respiratory or skin symptoms
Contact allergens affect the contact site

Autoimmune Diseases

Originate from initiating events in genetically predisposed individuals.
Central tolerance develops during embryonic periods. Peripheral tolerance is maintained via regulatory T lymphocytes and antigen-presenting dendritic cells.
Examples: Heparin-induced thrombocytopenia (autoantibodies destroy platelets), Systemic lupus erythematosus (SLE, chronic, multisystem inflammatory disease with autoantibody production.)

Alloimmunity

Immune reaction against antigens on other members' tissues (e.g., organ transplants, blood transfusions).
Examples include transient neonatal diseases (maternal immune system reacting to fetal antigens), transplant rejection.

Immune Deficiencies

Disorders from impaired immune or inflammatory response, phagocytes, or complement.
Deficiencies are either congenital (primary) (genetic defects disrupt lymphocyte development) or acquired (secondary) (secondary to disease or other physiological alterations).
Clinical hallmark: a propensity for unusual or recurrent severe infections.
Types of infection depend on the specific immune defect.

Infectious Diseases (Chapter 10)

Infectious disease is a significant cause of morbidity and mortality worldwide
Pathogens have features influencing their ability to overcome body defenses.
Stages of infection: incubation, prodromal, invasion, convalescence
Bacteria cause infections using virulence factors (e.g. pili, flagella, capsules, toxins).
Viruses are intracellular parasites.

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Description

Explore the roles of macrophages and the impact of age on the immune system. This quiz covers the activation of macrophages by interferon-γ, the formation of immunologic memory, and age-related factors in pediatric and geriatric populations. Test your knowledge on key concepts in immunology.