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?

<p>By interfering with host cell metabolism. (D)</p> Signup and view all the answers

What is a possible consequence of defects in phagocyte function?

<p>Recurrent life-threatening infections. (C)</p> Signup and view all the answers

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

<p>IFN-γ activates macrophages, causing them to produce proinflammatory cytokines and kill infected cells. (B)</p> Signup and view all the answers

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

<p>Decreased blood flow into the affected area (C)</p> Signup and view all the answers

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

<p>Memory cells differentiate into effector cells upon re-exposure to a specific antigen. (A)</p> Signup and view all the answers

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

<p>The T cell-dependent immune response develops gradually during the first 6 months of life. (A)</p> Signup and view all the answers

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

<p>Opsonization and phagocytosis of target cells by macrophages. (A)</p> Signup and view all the answers

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

<p>They involve the formation of immune complexes that deposit in target tissues. (A)</p> Signup and view all the answers

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

<p>Decreased neutrophil chemotaxis (A)</p> Signup and view all the answers

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

<p>Type I reactions are mediated by IgE antibodies, while Type II reactions are mediated by IgG or IgM antibodies. (A)</p> Signup and view all the answers

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

<p>Complement cascade (A)</p> Signup and view all the answers

What causes hyperacute graft rejection?

<p>Preexisting antibodies (A)</p> Signup and view all the answers

What is a common treatment for deficient antibody production?

<p>Gamma-globulin replacement therapy (C)</p> Signup and view all the answers

Which condition represents a cause of acquired immunodeficiencies?

<p>Aging (D)</p> Signup and view all the answers

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

<p>Primary immune deficiency (A)</p> Signup and view all the answers

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

<p>Immediate immune response (B)</p> Signup and view all the answers

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

<p>Bacteria of the Neisseria spp. (A)</p> Signup and view all the answers

Which of the following is treated by replacing host lymphocytes?

<p>Bone marrow failure (A)</p> Signup and view all the answers

What primarily causes primary immune deficiencies?

<p>Genetic defects (D)</p> Signup and view all the answers

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

<p>Secondary immune deficiency (A)</p> Signup and view all the answers

What is the clinical hallmark of immune deficiency?

<p>Propensity to unusual or recurrent severe infections (D)</p> Signup and view all the answers

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

<p>Fungal infections (A)</p> Signup and view all the answers

What is a defining feature of severe combined immunodeficiency?

<p>Total lack of T-cell function and severe lack of B-cell function (B)</p> Signup and view all the answers

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

<p>DiGeorge syndrome (A)</p> Signup and view all the answers

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

<p>Cell wall (B)</p> Signup and view all the answers

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

<p>Convalescence (A)</p> Signup and view all the answers

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

<p>To maintain tolerance to self and beneficial foreign tissues (B)</p> Signup and view all the answers

Which type of hypersensitivity reaction is primarily mediated by IgE?

<p>Type I hypersensitivity reactions (C)</p> Signup and view all the answers

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

<p>Variety of autoantibodies (B)</p> Signup and view all the answers

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

<p>Provide passive immunity (D)</p> Signup and view all the answers

What distinguishes type III hypersensitivity reactions from other types?

<p>They are mediated by immune complexes formed from circulating antibodies (C)</p> Signup and view all the answers

Which condition is an example of an alloimmune disorder?

<p>Transfusion reactions (D)</p> Signup and view all the answers

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

<p>Type IV hypersensitivity (A)</p> Signup and view all the answers

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

<p>Fruits (C)</p> Signup and view all the answers

What is the main characteristic of type IV hypersensitivity reactions?

<p>They are mediated by T cells and do not involve antibodies (A)</p> Signup and view all the answers

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

<p>Increased susceptibility to infections (B)</p> Signup and view all the answers

What role do allergens play in the immune system?

<p>They are specific antigens that trigger allergic responses (B)</p> Signup and view all the answers

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

<p>Genetic predisposition combined with an initiating event (B)</p> Signup and view all the answers

Heparin-induced thrombocytopenia primarily results from which mechanism?

<p>Heparin binding leading to the formation of autoantibodies (B)</p> Signup and view all the answers

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

<p>Antibody-mediated hypersensitivity (A)</p> Signup and view all the answers

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

<p>Increased levels of circulating autoantibodies (D)</p> Signup and view all the answers

What is the result of ingesting airborne allergens?

<p>Respiratory tract manifestations (D)</p> Signup and view all the answers

Flashcards

Passive Immunity in Newborns

Maternal IgG antibodies, transferred across the placenta, provide the newborn with passive immunity for the first 6 months.

Impaired Wound Healing in Elderly

In the elderly, wound healing slows down due to age-related decline in overall health and chronic conditions.

Immune System and Aging

The immune system's ability to distinguish between self and non-self weakens with age, leading to an increased risk of autoimmune disorders.

Hypersensitivity

An exaggerated immune response to harmless environmental antigens.

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Autoimmunity

The immune system attacks the body's own tissues because it mistakenly identifies them as foreign.

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Alloimmunity

The immune system responds to antigens from another individual, such as during organ transplantation or blood transfusions.

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Allergic Reactions Manifestation

Allergic reactions usually appear in the area of initial exposure to the allergen. For example, ingested allergens cause gastrointestinal symptoms.

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Autoimmune Disease Development

A genetic predisposition is necessary for an individual to develop an autoimmune disease, but a triggering event must also occur.

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Types of Hypersensitivity

Allergy, autoimmunity, and alloimmunity are all examples of hypersensitivity reactions.

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Allergen

A substance that triggers an allergic response by binding to IgE antibodies.

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Type I Hypersensitivity

A type of hypersensitivity reaction mediated by IgE antibodies and mast cells.

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Heparin-Induced Thrombocytopenia (HIT)

A condition where heparin, a blood thinner, triggers the formation of antibodies that attack platelets, leading to both bleeding and clotting.

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Systemic Lupus Erythematosus (SLE)

A chronic autoimmune disorder characterized by the production of a wide range of autoantibodies.

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Immunologic Memory

A type of immune response where immune cells like T and B cells create long-lived copies of themselves called memory cells.

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Macrophage Activation by IFN-γ

Macrophages become activated by interferon-gamma (IFN-γ), which is a signal from T helper 1 cells (Th1). These activated macrophages release inflammatory chemicals and kill infected cells.

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Type II Hypersensitivity Reactions

Type II (tissue-specific) hypersensitivity reactions are triggered by antibodies targeting specific cells or tissues. This can lead to various damaging effects like cell lysis, antibody-dependent cell-mediated cytotoxicity, and modulation of cell function.

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Type III Hypersensitivity Reactions

Type III (immune complex-mediated) hypersensitivity is caused by immune complexes that get deposited in tissues. These complexes activate the complement system, attracting neutrophils and causing inflammation.

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Histamine and Allergic Reactions

Histamine is a chemical released by mast cells and basophils, involved in various immediate allergic reactions like contraction of bronchial muscles (bronchoconstriction), increased vascular permeability (edema), and increased blood flow (vasodilation).

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Macrophage Activity

When activated, macrophages become powerful fighters against infections. They engulf and kill infected cells within their phagolysosomes.

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Neonate Immune System

A newborn's immune system is developing, and their inflammatory response may be weaker compared to adults. This is especially true for neutrophil chemotaxis and some complement pathway activity.

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T-cell Dependent and Independent Responses in Neonates

While the T-independent immune response is sufficient early in life, the T-dependent immune response takes time to develop fully, taking about 6 months for optimal function.

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Immune deficiency

A condition where the body's immune system is unable to function properly, leaving it vulnerable to infections and diseases.

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Primary immune deficiencies

Immune deficiencies are present at birth due to genetic defects affecting the immune system.

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Acquired immune deficiencies

Immune deficiencies that develop after birth due to various factors like infections, malnutrition, or aging.

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C3 deficiency

A type of immune deficiency caused by a lack of the C3 protein, a key component of the complement system, leading to recurrent and severe bacterial infections.

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Antibody deficiency

A type of immune deficiency characterized by a lack of specific antibody production, making the body susceptible to infections.

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Lymphocyte deficiency

A type of immune deficiency where the body's ability to produce healthy lymphocytes is impaired, often leading to severe infections.

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Hyperacute graft rejection

A serious reaction that occurs immediately after an organ transplant, often resulting in rapid rejection of the transplanted organ.

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Acute graft rejection

An immune reaction that occurs days to months after an organ transplant, leading to the eventual rejection of the transplanted organ.

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Septicemia and Septic Shock

Toxins released by bacteria in the bloodstream can damage blood vessel walls, leading to fluid leakage, low blood pressure, and potentially septic shock.

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Viruses as Intracellular Parasites

Viral infections involve viruses entering host cells and using the cell's resources to replicate, ultimately damaging the host cell.

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Exotoxins: Bacterial Weapons

Exotoxins are proteins secreted by bacteria that can directly damage cells, like destroying cell membranes or disrupting protein synthesis.

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Endotoxins: Internal Bacterial Trouble

Endotoxins, components of bacterial cell walls, trigger a strong inflammatory response when released into the body, leading to fever and other symptoms.

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Phagocyte Dysfunction and Infection

Defects in phagocytes, the immune cells that engulf and destroy pathogens, can result in recurrent infections due to impaired pathogen elimination.

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Primary immune deficiency

A type of immune deficiency caused by genetic defects that disrupt the development of lymphocytes.

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Secondary immune deficiency

A type of immune deficiency caused by factors like infections, diseases, or treatments that weaken the immune system.

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Unusual or recurrent severe infections

A common symptom of immune deficiency, characterized by recurring and severe infections that are unusual for a healthy person.

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Cell-mediated immune response

The immune system's ability to fight fungal and viral infections, often compromised in individuals with defects in cell-mediated immunity.

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Humoral immune response

The immune system's ability to fight bacterial infections, often compromised in individuals with defects in humoral immunity or complement function.

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Severe combined immunodeficiency (SCID)

A severe form of immune deficiency characterized by a complete lack of T-cell function and a severe (partial or total) lack of B-cell function.

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DiGeorge syndrome (chromosome 22q11.2 deletion syndrome)

A genetic disorder affecting the development of the thymus, parathyroid glands, and heart, leading to impaired T-cell immunity and other health issues.

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Defects in B-cell function

A broad category of disorders involving defects in B-cell function, ranging from impaired antibody production to complete absence of B-cells.

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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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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.

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