The Alternative Pathway in Immunity
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Questions and Answers

Which complement protein is primarily responsible for inactivating C1r and C1s, thereby halting the classical pathway?

  • C4b-binding protein (C4BP)
  • Membrane cofactor protein (MCP)
  • Complement receptor type 1 (CR1)
  • C1-inhibitor (C1INH) (correct)
  • Which complement regulator is the most efficient cofactor for factor I-mediated cleavage of C3b?

  • Decay accelerating factor (DAF)
  • C4b-binding protein (C4BP)
  • Membrane cofactor protein (MCP) (correct)
  • Complement receptor type 1 (CR1)
  • Which complement regulator can dissociate C4b2a complexes, thereby causing the cessation of the classical pathway?

  • C4b-binding protein (C4BP) (correct)
  • Membrane cofactor protein (MCP)
  • Decay accelerating factor (DAF)
  • Complement receptor type 1 (CR1)
  • Which complement regulator is found on virtually all epithelial and endothelial cells, except erythrocytes?

    <p>Membrane cofactor protein (MCP)</p> Signup and view all the answers

    Which complement regulator is a large polymorphic glycoprotein found mainly on peripheral blood cells?

    <p>Complement receptor type 1 (CR1)</p> Signup and view all the answers

    Which complement regulator is capable of combining with either fluid-phase or bound C4b, to prevent C4b from binding to C2?

    <p>C4b-binding protein (C4BP)</p> Signup and view all the answers

    What is the main function of the Membrane Inhibitor of Reactive Lysis (MIRL) or CD59?

    <p>To bind to C8 and prevent insertion of C9 into host cell membranes</p> Signup and view all the answers

    What is the role of the S protein (also known as vitronectin) in the regulation of terminal complement components?

    <p>It interacts with the C5b67 complex and prevents it from binding to cell membranes</p> Signup and view all the answers

    Which of the following is true about the complement receptors found on host cells?

    <p>They amplify and enhance the immune response by augmenting phagocytosis and stimulating accessory cells</p> Signup and view all the answers

    What is the relationship between the activation of complement and the inflammatory response?

    <p>Activation of complement is a very effective means of amplifying the inflammatory response to destroy and clear foreign antigens</p> Signup and view all the answers

    Which of the following is a function of the Membrane Inhibitor of Reactive Lysis (MIRL) or CD59?

    <p>To bind to C8 and prevent the insertion of C9 into host cell membranes</p> Signup and view all the answers

    What is the role of complement proteins in the immune system?

    <p>Complement proteins serve as a means of linking innate and natural immunity, as well as amplifying the inflammatory response to destroy and clear foreign antigens</p> Signup and view all the answers

    What is the function of Factor D in the complement system?

    <p>To cleave factor B into two pieces</p> Signup and view all the answers

    Which of the following is NOT a triggering substance for the alternative pathway of complement activation?

    <p>Lectins</p> Signup and view all the answers

    What is the role of lectins in the lectin pathway of complement activation?

    <p>Recognize carbohydrates on microbial cell walls</p> Signup and view all the answers

    What is the main difference between the lectin pathway and the alternative pathway of complement activation?

    <p>Involvement of lectins</p> Signup and view all the answers

    Why is Factor D essential in the complement system?

    <p>To cleave factor B, initiating complement activation</p> Signup and view all the answers

    What distinguishes the mannose-binding lectin pathway from the other complement pathways?

    <p>Carbohydrate recognition by lectins</p> Signup and view all the answers

    What is the primary function of mannose-binding lectin (MBL) in the lectin pathway?

    <p>To bind to mannose or related sugars found on the surface of pathogens, initiating the lectin pathway</p> Signup and view all the answers

    Which of the following statements about MBL is correct?

    <p>MBL deficiencies have been associated with serious infections in neonates and infants</p> Signup and view all the answers

    Which of the following MBL-associated serine proteases (MASPs) is involved in the activation of the lectin pathway?

    <p>MASP-2</p> Signup and view all the answers

    What is the primary function of C1 inhibitor (C1INH) in the complement system?

    <p>To inhibit the activation of the classical and lectin pathways at the first stages</p> Signup and view all the answers

    What is the primary reason for the regulation of the complement system?

    <p>To ensure that the reaction remains localized and infectious agents, not self-antigens, are destroyed</p> Signup and view all the answers

    Which of the following statements about the lectin pathway is correct?

    <p>The lectin pathway is initiated by the binding of MBL to mannose or related sugars found on pathogens</p> Signup and view all the answers

    What is the main role of opsonins in the immune response?

    <p>Facilitating destruction by phagocytic cells</p> Signup and view all the answers

    Which complement protein is considered the most potent anaphylatoxin?

    <p>C5a</p> Signup and view all the answers

    What effect does binding of C5a to basophils and mast cells have?

    <p>Increasing vascular permeability and causing smooth muscle contraction</p> Signup and view all the answers

    Which cells does C5a act as a chemotaxin for?

    <p>Neutrophils, basophils, and eosinophils</p> Signup and view all the answers

    Which effector molecules are produced by neutrophils upon C5a binding?

    <p>Oxygen radicals and hydrolytic enzymes</p> Signup and view all the answers

    How do anaphylatoxins contribute to the immune response?

    <p>Increasing vascular permeability</p> Signup and view all the answers

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