The Complement System
49 Questions
15 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the complement system?

It’s a system of proteins that’s activated by the presence of pathogens. It’s made up of a large system of different plasma proteins that interact with one another

Most of the protein components are ____ enzymes that become active ONLY after ______.

Most of the protein components are inert enzymes that become active ONLY after cleavage

Which of the following is considered an adaptive pathway in the complement system?

  • Lectin
  • Classical (correct)
  • Alternative
  • More than one above

    • The classical pathway is activated by _______ bound to foreign antigens

    <p>The classical pathway is activated by antibodies bound to foreign antigens.</p> Signup and view all the answers

    What role does it play in immunity?

    <p>It generates biological active molecules important for full inflammatory response</p> Signup and view all the answers

    Each complement system pathway depends on different types of _______ for their initiation

    <p>Each complement system pathway depends on different types of molecules for their initiation</p> Signup and view all the answers

    All three pathways converge to generate the same set of _____ complement components; which is _______

    <p>All three pathways converge to generate the same set of effector complement components; which is C3 convertase</p> Signup and view all the answers

    How do complement components contribute to the recruitment of immune cells?

    <p>By acting as chemoattractants for phagocytic cells</p> Signup and view all the answers

    What is the primary function of the activated complement proteins during opsonization?

    <p>To bind covalently to pathogens and target them for phagocytosis</p> Signup and view all the answers

    Which outcome is NOT associated with the activation of the complement system?

    <p>Immediate neutralization of toxins produced by pathogens</p> Signup and view all the answers

    In what way does the complement system enhance the adaptive immune response?

    <p>By opsonizing microbes for easier uptake by antigen-presenting cells</p> Signup and view all the answers

    What mechanism does the complement system use to kill microbes?

    <p>Pore formation in the microbial membrane leading to lysis</p> Signup and view all the answers

    The order of discovery of the nomenclature of complement components is ..

    <p>C1, C4, C2, C3, C5, C6, C7, C8, C9</p> Signup and view all the answers

    Which of the following correctly describes a unique aspect of the nomenclature of complement components in the alternative pathway, as opposed to the classical pathway?

    <p>Complement components in the alternative pathway are designated by letters (e.g., Factor B and Factor D), while those in the classical pathway are numbered (e.g., C1, C4).</p> Signup and view all the answers

    The products of complement cleavage are designated by addition of a lower case letter. The smaller cleavage fragment is designated “b” and the larger cleavage fragment is designated “a”

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

    In the complement system, most cleavage products follow the convention where the larger fragment is labeled "b" and the smaller fragment is labeled "a." Which of the following describes the exception seen with C2 cleavage?

    <p>C2 is the only component where the smaller fragment is labeled &quot;b&quot; and the larger fragment is labeled &quot;a.&quot;</p> Signup and view all the answers

    Which of the following proteins is responsible for initiating the classical pathway of complement activation?

    <p>C1</p> Signup and view all the answers

    C1 can bind to the surface of pathogens in three different ways. Which of the following is NOT one of those mechanisms?

    <p>Binding to mannose residues on pathogen surface</p> Signup and view all the answers

    Out of the three ways C1 can bind to the surface of pathogens, which one is the most effective initiation? (Was in red)

    <p>Binds to antigen-antibody complexes on pathogen surface</p> Signup and view all the answers

    The lectin pathway of complement activation is initiated when

    <p>Mannose Binding lectin (MBL) or ficolins bind to specific carbohydrate structures, like mannose or N-acetylglucosamine, on the surface of microbes</p> Signup and view all the answers

    The alternative pathway of complement activation is initiated when

    <p>Spontaneous hydrolysis of C3 produces derived plasma C3b, which then binds to microbial surfaces</p> Signup and view all the answers

    The carbohydrate-binding proteins of the lectin pathway include ….

    <p>They include Mannose binding lectin and ficolins</p> Signup and view all the answers

    In each pathway, sequential reactions lead to generation of a protein complex called ____

    <p>C3 convertase</p> Signup and view all the answers

    In the complement cascade, what’s the primary function of C3b, and how does C3a contribute to the immune response, respectively?

    <p>C3b acts as an opsonin, tagging pathogens for destruction, while C3a serves as a mediator of inflammation by promoting immune cell recruitment.</p> Signup and view all the answers

    C3a acts as an opsonin, tagging pathogens for destruction, while C3b serves as a mediator of inflammation by promoting immune cell recruitment

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

    In the classical complement pathway, which immunoglobulins are the most potent activators, and how do they initiate the cascade?

    <p>IgM and IgG activate the classical pathway by binding C1q after they attach to antigens on pathogen surfaces</p> Signup and view all the answers

    The backbone of C1 is made up of __

    <p>C1q</p> Signup and view all the answers

    How is C1 activated in the classical pathway of the complement system?

    <p>It is activated when two globular heads of C1q bind two adjacent Fc regions of the antibodies bound to an antigen</p> Signup and view all the answers

    Describe events of the classical pathway cascade starting at after C1 activation

    <p>After C1 is activated, C1r cleaves itself, then cleaves adjacent C1s molecules, which activates protease activity of C1s. C1s cleaves C4 to C4a and C4b. C4b then covalently attaches to microbe/Ab-Ag complex. Then C1s cleaves C2 to C2b and C2a (large). C2a then binds to C4b forming the complex C4b2a on the surface of the microbe. This C4b2a is the classical pathways C3 convertase. C3 convertase cleaves C3 into C3a and C3b, then C3b attaches to the microbes. It’s now tagged for destruction by phagocytes micros</p> Signup and view all the answers

    Classical pathway: After C3b attaches to the surface to the pathogen (opsonization), what does C3b form a complex with?

    <p>It forms a complex with C3 convertase to form C5 convertase</p> Signup and view all the answers

    The lectin pathway is an independent innate immune response

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

    MBL is a tetrametric member of C-type lectin family, but doesn’t have structural similarities with C1q

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

    In the lectin pathway of complement activation, what does MBL recognize and bind to on the surface of pathogens?

    <p>Mannose, fructose, and N-acetylglucosamine residues</p> Signup and view all the answers

    In the lectin pathway of complement activation, what happens to Mannose-Binding Lectin (MBL) after it binds to a microbial cell wall?

    <p>MBL undergoes a conformational change, which activates MBL-associated serine proteases (MASPs) that cleave C4 and C2</p> Signup and view all the answers

    Which statement best describes the role of C5b in the complement cascade?

    <p>It initiates the assemble y of the Membrane attack complex</p> Signup and view all the answers

    C3 is the most abundant complement protein and a key player in all pathways

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

    What complex functions as the alternative C3 convertase in the alternative complement pathway?

    <p>C3bBb</p> Signup and view all the answers

    What does the alternative complement pathway utilize to initiate the cascade?

    <p>Spontaneous cleavage of C3</p> Signup and view all the answers

    In the alternative pathway, spontaneous cleavage of C3 results in which of the following events?

    <p>C3b binds to microbial surfaces and forms a complex with Factor B</p> Signup and view all the answers

    In the alternative pathway of complement activation, how is C3 convertase (C3bBb) stabilized on the microbial surface?

    <p>By Properdin</p> Signup and view all the answers

    The C5 convertase generated by all complement pathways initiate the formation of what?

    <p>It initiates the formation of the Membrane Attack Complex</p> Signup and view all the answers

    How do the C5 convertases from the classical, lectin and alternative pathway contribute to the initiation of the MAC formation?

    <p>All C5 convertases cleave C5 into C5b, which initiates the assembly of the MAC by binding to the target membrane</p> Signup and view all the answers

    How do complement control proteins help regulate complement activation?

    <p>By inhibiting the protease activities of complement components to prevent excessive activation</p> Signup and view all the answers

    Which complement pathway is regulated by Factor H, Factor I and Decay-Accelerating Factor (CD55)?

    <p>Alternative pathway</p> Signup and view all the answers

    How do Factor H and Factor I regulate the alternative pathway compared to CD55?

    <p>Factor H and Factor I bind to C3b, promoting its degradation and preventing further complement activation, while CD55 accelerates the decay of the C3 convertase (C3bBb) directly.</p> Signup and view all the answers

    How does Decay Accelerating Factor (CD55) regulate the alternative complement pathway?

    <p>CD55 accelerates the decay of C3 convertase (C3bBb), thereby preventing prolonged activation of the alternative pathway.</p> Signup and view all the answers

    Which of the following complement control protein acts on both the classical and lectin pathway?

    <p>C1 inhibitor</p> Signup and view all the answers

    How does the complement control protein C1 inhibitor regulate both the classical and lectin pathways of complement activation?

    <p>By inhibiting the activity of C1r and C1s in the classical pathway, and MASPs (MBL-associated serine proteases) in the lectin pathway.</p> Signup and view all the answers

    Why do C3 deficient dogs develop renal failure later in life?

    <p>C3 deficient dogs develop renal failure due to the complement system being unable to clear immune complexes effectively. Over time, the inability of C3b to facilitate the dissociation and clearance of immune complexes leads to their deposition in the kidneys.</p> Signup and view all the answers

    Study Notes

    Complement System Protection Mechanisms

    • Complement proteins act as chemoattractants, drawing phagocytic cells to sites of activation, enhancing immune response.
    • Activated complement proteins bind covalently to pathogens, a process known as opsonization, marking them for phagocytosis.
    • Final complement activation components create pores in microbial membranes, leading to microbial cell lysis and death.

    Role in Adaptive Immunity

    • Complement system supports adaptive immunity by enhancing the uptake of pathogens by antigen-presenting cells, such as dendritic cells.
    • B cells possess receptors for specific complement proteins, improving their response to microbes that have been opsonized with complement components.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    Self study questions

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser