Immunology Chapter: Innate and Adaptive Defenses
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Questions and Answers

What role do anaphylotoxins play in inflammation?

  • They limit the recruitment of macrophages.
  • They activate the adaptive immunity directly.
  • They bind to receptors on various immune cells. (correct)
  • They initiate cell lysis through the membrane attack complex.

What is a consequence of complement deficiencies in individuals?

  • Increased resistance to infections.
  • Decreased activation of neutrophils.
  • Enhanced inflammatory response.
  • Higher likelihood of developing autoimmune diseases. (correct)

What condition is most commonly associated with classical pathway deficiencies in complement?

  • Multiple sclerosis.
  • Rheumatoid arthritis.
  • Psoriasis.
  • Systemic Lupus Erythematosus (SLE). (correct)

How do anaphylotoxins influence immune cell activity?

<p>By recruiting and activating immune cells. (B)</p> Signup and view all the answers

Which of the following best describes pseudopodia?

<p>Extensions of the cell membrane that assist in movement or engulfing. (B)</p> Signup and view all the answers

How many types of Toll-like receptors are there?

<p>10 (D)</p> Signup and view all the answers

Which cell type is most important in phagocytosis following an infection?

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

What triggers the classical pathway of complement activation?

<p>Complexes containing IgM or IgG (A)</p> Signup and view all the answers

What role does C3b play in phagocytosis?

<p>It makes bacteria more likely to be phagocytosed. (D)</p> Signup and view all the answers

What is the function of the plasma proteins in the complement system?

<p>They circulate inactive until activated. (C)</p> Signup and view all the answers

Which receptor type does C3b bind to on phagocytes?

<p>Complement receptor type I (CR1) (D)</p> Signup and view all the answers

What is a primary characteristic of neutrophils during an infection?

<p>They migrate to the site of infection. (A)</p> Signup and view all the answers

What is the central component in the complement system?

<p>C3 (B)</p> Signup and view all the answers

What triggers a series of events that leads to inflammation in the complement system?

<p>Antigen-antibody complexes (C)</p> Signup and view all the answers

Which protein can activate phagocytosis through C5a?

<p>C3b (B)</p> Signup and view all the answers

What is NOT a characteristic of innate defenses?

<p>Adapts based on experience (A)</p> Signup and view all the answers

Which of the following is a physical barrier in innate defenses?

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

How do pattern recognition receptors (PRRs) function in the immune system?

<p>They identify structures shared by classes of microbes (B)</p> Signup and view all the answers

What does the presence of Toll-like receptors indicate?

<p>Innate ability to detect pathogen-associated molecular patterns (B)</p> Signup and view all the answers

Which of the following is NOT involved in internal defenses?

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

What is a key difference between innate and adaptive immunity?

<p>Innate immunity is immediately present but adaptive takes time to develop (B)</p> Signup and view all the answers

Which molecule is NOT a pathogen-associated molecular pattern (PAMP)?

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

What role do natural killer cells play in innate immunity?

<p>They destroy infected or tumor cells (D)</p> Signup and view all the answers

What role do Natural Killer Cells play in the immune response?

<p>They recognize and directly attack cancerous cells. (D)</p> Signup and view all the answers

What do PAMPs correspond to in the immune system?

<p>Molecules found on pathogens that are recognized by PRRs. (D)</p> Signup and view all the answers

What is the result of impaired inflammatory response due to deficiency?

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

How does complement activation enhance immune responses?

<p>By enhancing opsonization, chemotaxis, and MAC formation. (A)</p> Signup and view all the answers

What function do fluid-phase regulators serve in the context of the complement system?

<p>They protect host cells from complement attack. (C)</p> Signup and view all the answers

What happens when a cell is invaded by a pathogen?

<p>It triggers a response from Natural Killer Cells. (C)</p> Signup and view all the answers

What is a consequence of successful complement activation?

<p>Direct lysis of pathogens through MAC formation. (B)</p> Signup and view all the answers

Which of the following statements is incorrect regarding susceptibility due to immune deficiency?

<p>It enhances the body's ability to deal with existing pathogens. (C)</p> Signup and view all the answers

Flashcards

Complement System

A group of proteins in the blood that work together to fight infections. They help to kill bacteria, viruses, and other pathogens.

Membrane Attack Complex (MAC)

A structure formed by complement proteins that punches holes in the membranes of bacteria, viruses, and other pathogens, causing them to burst and die.

Anaphylatoxins

Complement proteins that trigger inflammation by activating mast cells, basophils, and other immune cells.

Complement Deficiency

A condition in which the complement system is not working properly, making individuals more susceptible to infections and autoimmune diseases.

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Classical Pathway

One of the three main pathways of complement activation. This pathway is triggered by antibodies bound to an antigen.

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Innate Immunity

The body's first line of defense against pathogens, present from birth, providing an immediate and non-specific response.

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Physical Barriers

The first line of defense against pathogens, including skin, mucous membranes, and body fluids like tears and saliva.

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Internal Defenses

The second line of defense against pathogens, including phagocytic cells, complement proteins, and natural killer cells.

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Phagocytosis

The process by which immune cells engulf and destroy pathogens.

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Pattern Recognition Receptors (PRRs)

Receptors on immune cells that recognize specific patterns found on pathogens.

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Pathogen-Associated Molecular Patterns (PAMPs)

Molecular structures found on pathogens that are recognized by PRRs.

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Toll-like Receptors (TLRs)

A type of PRR found on immune cells that recognizes various PAMPs, including those from bacteria, viruses, and fungi.

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NOD-like Receptors (NLRs)

A type of PRR located inside the cell that recognizes PAMPs from intracellular bacteria.

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Natural Killer Cells

Immune cells that are not phagocytes and destroy cells that have lost or modified surface structures, often due to viral infection or cancer. They are part of the innate immune system.

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PAMPs

Pathogen-associated molecular patterns (PAMPs) are molecules found on pathogens that are recognized by the immune system as foreign. They activate immune responses.

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PRRs

Pattern recognition receptors (PRRs) are receptors on immune cells that recognize PAMPs and trigger defense mechanisms against pathogens. They are part of the innate immune system.

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Opsonization

The process of coating pathogens with molecules, like antibodies or complement proteins, to make them more attractive to phagocytes.

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Chemotaxis

The movement of immune cells towards a chemical attractant, such as the site of an infection.

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Complement Regulators

Proteins that help to prevent the complement system from attacking healthy host cells, like CD59 and factor H.

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What are the major cells involved in phagocytosis?

Macrophages and neutrophils are the primary phagocytes. They ingest and destroy pathogens.

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How does the Complement system activate?

The activation of the complement system involves a series of protein interactions that lead to the formation of a membrane attack complex (MAC), which punches holes in the membranes of bacteria, viruses, and other pathogens.

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What are the functions of the Complement system?

The complement system plays a crucial role in fighting infections through opsonization, direct lysis of pathogens, and recruitment of immune cells to the site of infection.

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C3 Convertase

A key enzyme in the complement system. It cleaves C3, a complement protein, into C3a and C3b. This is an important step in the activation cascade.

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Study Notes

Innate Defenses

  • Quick reaction, born with it
  • Physical barriers: tight junctions at epithelial cells, mucous membranes, stomach acidity (pH), antimicrobial secretion (lysosome in tears)
  • Internal defenses: phagocytosis, complement, NK cells, cytokine secretion

Adaptive Defenses

  • Humoral: B cells
  • Cell-mediated: T cells

Pathogen Recognition

  • Pattern Recognition Receptors (PRRs)
  • Encoded in germ line, limited diversity (born with it - one set)
  • Toll-like receptors (TLRs)
  • NOD-like receptors (NLRs)
  • Recognize structures shared by classes of microbes (molecular patterns - PAMPs)
  • Examples include peptidoglycan, lipopolysaccharide (LPS)

Toll-like Receptors (TLRs)

  • 10 types
  • Expressed by cells (e.g., macrophages, dendritic cells) on cell surface and membranes of intracellular vesicles
  • Jules Hoffmann discovered Toll receptors in Drosophila
  • Beutler identified mammalian TLR4 as the LPS receptor

Phagocytosis

  • Neutrophils and macrophages leave blood, move to infection site
  • Recognition, ingestion, and digestion of microbes
    • Phagosome formation
    • Phagolysosome formation
    • Digestion of ingested microbe
    • Discharge of waste

Complement System

  • 30 plasma proteins, circulate inactive
  • Activated by infection, triggers inflammation
  • Classical, lectin, and alternative pathways
  • Functions:
    • Opsonization (making microbes more susceptible to phagocytosis)
    • Cell lysis (rupturing membranes)
    • Inflammation
    • Stimulating adaptive immunity

Natural Killer (NK) Cells

  • Not phagocytes; part of the lymphoid lineage
  • Recognize if a cell is infected by a virus or cancerous (modified/lost surface structures)
  • Kill infected cells by releasing perforin (punches holes), granzyme (enters via perforin pore), and inducing apoptosis (programmed cell death)

PAMPs and PRRs

  • Pathogen-associated molecular patterns (PAMPs) are molecules found on pathogens.
  • Pattern recognition receptors (PRRs) recognize PAMPs on immune cells, initiating immune defense mechanisms.
  • Deficiency in PRRs can lead to impaired immune response and difficulty clearing infections.
  • Regulatory proteins (e.g., CD59, CD55) prevent excessive complement activation and protect host cells.
  • Complement activation enhances immune responses through opsonization, chemotaxis, and direct lysis of pathogens.

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Innate Immune System PDF

Description

Explore the dual mechanisms of the immune system with this quiz focusing on innate and adaptive defenses. Test your knowledge of physical barriers, pathogen recognition through PRRs, and the roles of B and T cells in adaptive immunity. Ideal for students studying immunology or related fields.

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