Immunology and Phagocytosis Quiz

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Questions and Answers

What is the first step in the process of phagocytosis?

Formation of a phagosome

Digesting the particles

Attachment of the phagocyte to the target (correct)

Fusion with a lysosome

Which immune cells are responsible for immune surveillance?

Natural killer (NK) cells (correct)

Macrophages

T cells

B cells

How do interferons primarily function in the immune response?

They destroy viruses directly.

They activate complement proteins.

They trigger the production of antiviral proteins in normal cells. (correct)

They enhance phagocytic activity.

What distinguishes tumor-specific antigens in cancer cells?

They are recognized by NK cells. Signup and view all the answers

Which pathway is activated when antibodies bind to invading organisms?

Classical pathway Signup and view all the answers

What role do perforins play in the function of NK cells?

They lyse the plasma membrane of abnormal cells. Signup and view all the answers

Which type of interferon is secreted by fibroblasts and slows inflammation?

Interferon beta (β) Signup and view all the answers

Which method does the alternative pathway utilize to activate the complement system?

Spontaneous binding of complement factors to invaders Signup and view all the answers

What is the primary mechanism involved in delayed hypersensitivity (Type IV)?

Cytokine activation of macrophages and cytotoxic T cells Signup and view all the answers

Which condition is an example of immune complex (type III) hypersensitivity?

Systemic lupus erythematosus (SLE) Signup and view all the answers

How does aging affect T cell responsiveness?

T cell responsiveness declines Signup and view all the answers

What happens to immune surveillance against tumor cells as a person ages?

It declines Signup and view all the answers

Which of the following statements about the immune system's interaction with the nervous and endocrine systems is true?

They adjust the sensitivity of the immune response Signup and view all the answers

What is the primary function of cytotoxic T cells (TC cells)?

Attack cells infected by viruses. Signup and view all the answers

Which of the following describes naturally acquired immunity?

Immunity inherited from the mother. Signup and view all the answers

What characteristic of the immune response allows the body to recognize previously encountered antigens?

Memory Signup and view all the answers

What type of immunity is characterized by the transfer of antibodies from one individual to another?

Passive immunity Signup and view all the answers

Which type of T cell is responsible for inhibiting the function of other T cells and B cells?

Suppressor T cells Signup and view all the answers

What role do MHC I proteins play in the immune response?

Transport abnormal peptides to the cell surface. Signup and view all the answers

Which of these properties of immunity refers to the ability to respond to various antigens?

Versatility Signup and view all the answers

What is the main role of helper T cells (TH cells) in the immune system?

Stimulate the function of T cells and B cells. Signup and view all the answers

What is the result of a defective adenosine deaminase (ADA) enzyme?

Accumulation of lethal metabolites to T cells Signup and view all the answers

Which of the following diseases is NOT classified as an autoimmune disease?

Asthma Signup and view all the answers

What characterizes immediate hypersensitivity reactions?

They can lead to anaphylactic shock Signup and view all the answers

What role do IL-4 and TH2 cells play in allergies?

They initiate the production of IgE antibodies Signup and view all the answers

What distinguishes delayed hypersensitivity from other hypersensitivities?

It is mediated by T cells Signup and view all the answers

Which condition is a result of a systemic allergic reaction?

Anaphylactic shock Signup and view all the answers

What defines subacute hypersensitivity reactions?

They involve IgM and IgG over a prolonged period Signup and view all the answers

What typically happens during a systemic allergic response?

Vasodilation leads to potential circulatory collapse Signup and view all the answers

What characterizes the primary immune response?

It occurs upon first exposure to an antigen and develops slowly. Signup and view all the answers

What is the primary difference between IgM and IgG during the primary immune response?

IgM is produced faster but is less effective than IgG. Signup and view all the answers

In what way does the secondary immune response differ from the primary response?

It produces antibodies more rapidly and in larger quantities due to memory cells. Signup and view all the answers

Which cells are activated to fight bacterial infections?

Neutrophils and NK cells. Signup and view all the answers

How do cytokines function in the immune system?

They serve as chemical messengers that coordinate various immune cell activities. Signup and view all the answers

What role do maternal IgG antibodies play before birth?

They cross the placenta to provide passive immunity to the fetus. Signup and view all the answers

What is one characteristic of tumor necrosis factors (TNFs)?

They slow tumor growth and can induce tumor cell death. Signup and view all the answers

What triggers the activation of cytotoxic T cells during a viral infection?

Interaction with virus-infected cells. Signup and view all the answers

What defines autoimmune disorders?

Activated B cells produce antibodies against normal body cells. Signup and view all the answers

What is the function of interleukins in the immune response?

They are involved in stimulating inflammation and scar tissue formation. Signup and view all the answers

At what stage of fetal development can the fetus produce an immune response?

At three to four months. Signup and view all the answers

What is the outcome of cytokine block treatments for autoimmune disorders?

They suppress the entire immune system. Signup and view all the answers

What is a role of colony-stimulating factors (CSFs) in the immune system?

To stimulate the production of blood cells in red bone marrow. Signup and view all the answers

What is the significance of activated macrophages in the immune response?

They secrete tumor necrosis factors (TNFs). Signup and view all the answers

Study Notes

Phagocytosis

Phagocytes attach to targets, engulf them to form phagosomes
Phagosomes fuse with lysosomes to form phagolysosomes
Lysosomal enzymes digest particles, leaving residual bodies
Residual bodies are expelled by exocytosis

Immune Surveillance

Carried out by natural killer (NK) cells
NK cells identify and attach to abnormal cells
NK cells use perforin vesicles to lyse abnormal plasma membranes
NK cells attack cancer cells and virus-infected cells

Cancer Cells

Tumor-specific antigens identify cancer cells
NK cells destroy cancer cells
Some cancer cells evade NK cells (immunological escape)

Viral Infections

Virus-infected cells display abnormal proteins
NK cells recognize and destroy these cells

Interferons (IFNs)

Family of immune modulating proteins
Released by lymphocytes, macrophages, and fibroblasts
Trigger production of antiviral proteins in normal cells
Block viral replication without killing viruses

Interferon Types

Interferon alpha (α): Produced by virus-infected cells, attracts and stimulates NK cells, enhances resistance to viral infection.
Interferon beta (β): Secreted by fibroblasts, slows inflammation in a damaged area.
Interferon gamma (γ): Secreted by T cells and NK cells, stimulates macrophage activity.

Complement System

Group of 30 complement (C) proteins in plasma
Enhance innate and adaptive defenses
Work together in cascades with three pathways

Complement Pathways

Classical Pathway: Antibodies bind to invaders and complement components, triggering activation cascade.
Lectin Pathway: Lectins bind to sugars on invaders, activating complement.
Alternative Pathway: Complement factors bind directly to invaders, activating the cascade.

Adaptive (Specific) Defenses

Cells Involved:
- T cells: Provide cell-mediated immunity, defending against abnormal cells and pathogens inside cells.
- B cells: Provide antibody-mediated immunity, defending against antigens and pathogens in body fluids.
Forms of Immunity:
- Innate: Present at birth.
- Adaptive: Develops after birth.
- Active: Antibodies develop after exposure to an antigen.
  - Naturally acquired: Through environmental exposure to pathogens.
  - Artificially induced: Through vaccines containing pathogens.
- Passive: Antibodies are transferred from another source.
  - Naturally acquired: Antibodies acquired from the mother.
  - Artificially induced: By injection of antibodies.
Properties of Immunity:
- Specificity: Each T or B cell responds only to a specific antigen.
- Versatility: The body produces many types of lymphocytes to fight different antigens. Active lymphocytes clone themselves.
- Memory: Some active lymphocytes (memory cells) stay in circulation, providing immunity against new exposure.
- Tolerance: The immune system ignores 'normal' antigens (self-antigens)

T Cells and Immunity

Major Types of T Cells:
- Cytotoxic T cells (TC cells): Attack virus-infected cells, responsible for cell-mediated immunity.
- Memory T cells: Clone themselves in response to a 'remembered' antigen.
- Helper T cells (TH cells): Stimulate the function of T cells and B cells.
- Suppressor T cells (TS cells): Inhibit the function of T cells and B cells.
Antigen Presentation: T cells recognize antigens bound to MHC proteins on plasma membranes.
MHC Proteins: Membrane glycoproteins that bind to antigens, genetically coded in chromosome 6 (major histocompatibility complex, MHC). Differ among individuals.
Classes of MHC Proteins:
- Class I: Found in membranes of all nucleated cells. Pick up small peptides and carry them to the surface. Abnormal peptides or viral proteins activate T cells to destroy the cell.
- Class II: Found in membranes of antigen-presenting cells (APCs) and lymphocytes. Prevents bacterial and viral adhesion.

Primary and Secondary Immune Responses

Primary Response:
- Occurs upon the first exposure to an antigen.
- Slow to develop, taking time for antigens to activate B cells and antibody titer to rise.
- Peak response takes about two weeks and declines rapidly.
- IgM is produced faster than IgG but is less effective.
Secondary Response:
- Triggered by subsequent exposure to the same antigen.
- More extensive and prolonged due to memory cells being primed.
- Memory B cells are activated at lower antigen concentrations and secrete antibodies in massive quantities.
- IgG rises very high and very quickly, remaining elevated for an extended time.
- IgM production is also quicker and slightly extended.

Combined Responses to Infections

Bacterial Infection:
- Neutrophils and NK cells kill bacteria.
- Cytokines draw phagocytes to the area.
- Antigen presentation activates helper T cells and cytotoxic T cells.
- B cells activate and differentiate.
- Plasma cells increase antibody levels.
Viral Infection:
- Similar to bacterial infection, but cytotoxic T cells and NK cells are activated by contact with virus-infected cells.

Immune System Development

Fetal Development:
- The fetus develops immunocompetence after exposure to antigens at about three to four months.
- Fetal thymus cells migrate to tissues that will form T cells.
- The liver and bone marrow produce B cells.
- A four-month fetus produces IgM antibodies.
Before Birth:
- Maternal IgG antibodies cross the placenta, providing passive immunity to the fetus.
After Birth:
- Mother's milk provides IgA antibodies while passive immunity from the mother is lost.
- The infant produces IgG antibodies through exposure to antigens.
- Antibody, B cell, and T cell levels slowly rise to adult levels by about age 12.

Cytokines of the Immune System

Definition: Chemical messengers involved in cellular immunity.
Examples: Interferons, interleukins, tumor necrosis factors (TNFs).
Interleukins:
- Functions:
  - Increase T cell sensitivity to antigens on macrophage membranes.
  - Stimulate B cell activity, plasma cell formation, and antibody production.
  - Enhance nonspecific defenses by stimulating inflammation, scar tissue formation by fibroblasts, elevating body temperature, stimulating mast cell formation, and promoting ACTH secretion.
  - Moderate the immune response by suppressing immune function and shortening the response.
- IL-1 and IL-2: Important in stimulating and maintaining the immune response by stimulating the activities of other immune cells and the secreting cell, creating a positive feedback loop that recruits more immune cells.
Tumor Necrosis Factors (TNFs):
- Slow tumor growth and kill tumor cells.
- Activated macrophages secrete one type of TNF and carry the molecules in their plasma membranes.
- Cytotoxic T cells produce a different type of TNF.
- Stimulate granular leukocyte production, promote eosinophil activity, cause fever, and increase T cell sensitivity to interleukins.
Phagocyte-Activating Chemicals:
- Coordinate immune defenses by adjusting phagocytic cell activities.
- Attract free macrophages and microphages and prevent their premature departure from the site of injury.
Colony-Stimulating Factors (CSFs):
- Produced by active T cells, cells of the monocyte--macrophage system, endothelial cells, and fibroblasts.
- Stimulate blood cell production in red bone marrow and lymphocyte production in lymphoid tissues and organs.
Classification by Origin:
- Lymphokines: Produced by lymphocytes.
- Monokines: Secreted by active macrophages and other APCs.
- Cells involved in adaptive immunity and tissue repair also secrete cytokines.

Immune Disorders

Types: Autoimmune disorders, immunodeficiency diseases, allergies.
Autoimmune Disorders
- Definition: Malfunction of the system that recognizes and ignores 'normal' antigens.
- Examples: Thyroiditis, rheumatoid arthritis, insulin-dependent diabetes mellitus (IDDM).
- Treatment: Suppressing the entire immune system, blocking cytokine action, blocking costimulatory molecules.
- Research: Focuses on activating regulatory T cells, inducing self-tolerance using vaccines, and directing antibodies against self-reactive immune cells.
- Mechanisms: Weakly self-reactive lymphocytes activated by foreign antigens resembling self-antigens, defective adenosine deaminase (ADA) enzyme
Autoimmune Diseases:
- The immune system loses the ability to distinguish self from foreign, producing autoantibodies and sensitized TC cells that destroy body tissues.
- Examples: Multiple sclerosis, myasthenia gravis, Graves' disease, type 1 diabetes mellitus, systemic lupus erythematosus (SLE), glomerulonephritis, rheumatoid arthritis.
Hypersensitivities:
- Definition: Immune responses to perceived harmless threats causing tissue damage.
- Types: Distinguished by time course and whether antibodies or T cells are involved.
  - Antibodies cause immediate and subacute hypersensitivities.
  - T cells cause delayed hypersensitivity.
- Immediate Hypersensitivity:
  - Acute (type I) hypersensitivities (allergies) begin seconds after contact with an allergen.
  - Initial contact is asymptomatic but sensitizes the person.
  - Reaction may be local or systemic.
  - The mechanism involves IL-4 secreted by TH2 cells, stimulating B cells to produce IgE, which binds to mast cells and basophils, causing a histamine release and an inflammatory response.
  - Subsequent encounters with the same allergen trigger an allergic reaction.
  - Reactions: Can be local or systemic
    - Local: Mast cells of the skin and respiratory and gastrointestinal mucosa release histamines, causing dilated and leaky blood vessels, leading to symptoms like a runny nose, hives, and watery eyes. Inhaled allergens can cause asthma, which is controlled with antihistamines.
    - Systemic: Anaphylactic shock.
- Anaphylactic Shock:
  - A systemic response to an allergen that enters the blood and circulates rapidly.
  - Basophils and mast cells throughout the body release histamine.
  - Can cause bronchiole constriction, tongue swelling, sudden vasodilation, fluid loss from the bloodstream, circulatory collapse (hypotensive shock), and death.
  - Treatment: Epinephrine.
- Subacute Hypersensitivities:
  - Caused by IgM and IgG transferred via blood plasma or serum.
  - Slow onset (1--3 hours) and long duration (10--15 hours).
  - Cytotoxic (type II) reactions: Antibodies bind to antigens on specific body cells, stimulating phagocytosis and complement-mediated lysis of cellular antigens. Example: mismatched blood transfusion reaction.
  - Immune complex (type III) hypersensitivity: Antigens are widely distributed in the body or blood. Insoluble antigen-antibody complexes form and cannot be cleared from a particular area. Intense inflammation, local cell lysis, and cell killing by neutrophils occur. Example: Systemic lupus erythematosus (SLE).
- Delayed Hypersensitivities (Type IV):
  - Slow onset (one to three days).
  - Mechanism depends on helper T cells.
  - Cytokine-activated macrophages and cytotoxic T cells cause damage.
  - Example: Allergic contact dermatitis (e.g., poison ivy). Agents act as haptens. The TB skin test depends on this reaction.

Effects of Aging on the Immune System

Immune System Decline:
- Increases vulnerability to infections and cancer.
Effects of Aging:
- Thymic hormone production is greatly reduced.
- T cells become less responsive to antigens.
- Fewer T cells reduce B cell responsiveness.
- Immune surveillance against tumor cells declines.

Immune System Integration

Nervous and Endocrine Systems:
- Interact with thymic hormones.
- Adjust the sensitivity of the immune response.

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Description

Test your knowledge on key concepts in immunology, including phagocytosis, immune surveillance by NK cells, and the role of interferons in viral infections. This quiz covers the mechanisms by which the immune system identifies and destroys cancerous and virus-infected cells. Challenge yourself and see how well you understand these critical processes.