Antibody Functions and Mechanisms
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Questions and Answers

What is the main mechanism of transport for molecules like mAb within a fluid?

  • Convection
  • Convention (correct)
  • Endocytosis
  • Receptor-mediated transport
  • What is the difference between phagocytosis and pinocytosis?

  • Phagocytosis occurs in cells, while pinocytosis occurs in tissues
  • Phagocytosis is the internalization of liquid phase molecules, while pinocytosis is the internalization of solid material
  • Phagocytosis is fast, while pinocytosis is slow
  • Phagocytosis is the internalization of solid material, while pinocytosis is the internalization of liquid phase molecules (correct)
  • How do mAb preferentially bind to antigens?

  • Non-specifically through the Fc portion to soluble antigens
  • Non-specifically through the Fc portion to cell surface antigens
  • Specifically through the Fab portion to soluble antigens (correct)
  • Specifically through the Fab portion to cell surface antigens
  • How are mAb eliminated from the body?

    <p>Through proteolysis, but the Fc receptor protects against catabolism</p> Signup and view all the answers

    Which type of mAb is degraded the fastest?

    <p>Murine mAb</p> Signup and view all the answers

    What determines the binding of mAb to antigens?

    <p>The kinetics of the binding</p> Signup and view all the answers

    What is the role of the Fc receptor in mAb?

    <p>It protects mAb against catabolism</p> Signup and view all the answers

    What is the consequence of high competition between mAb and the endogenous antigen ligand?

    <p>Reduced binding of mAb to the antigen</p> Signup and view all the answers

    What is the difference in the degradation rate between human and murine mAb?

    <p>Human mAb is degraded in weeks, while murine mAb is degraded in days</p> Signup and view all the answers

    What is the key factor in the binding of mAb to antigens?

    <p>The affinity of the mAb for the antigen</p> Signup and view all the answers

    Study Notes

    Complement-Dependent Cytotoxicity and Antibody Functions

    • Complement-dependent cytotoxicity (CDC) involves recognition of the Fc portion of antibodies, independent of specific antigen recognition.
    • Antibodies neutralize exotoxins and viruses by targeting specific structures on microorganisms.
    • Preventing bacterial adherence to host cells is a crucial antibody function.
    • The membrane attack complex (MAC) leads to cytolysis, facilitating cell destruction.
    • Agglutination is a process by which antibodies clump microorganisms together, enhancing their clearance.
    • Immobilization of bacteria and protozoa occurs through specific antibody binding.
    • Opsonization enhances phagocytosis by marking pathogens for destruction.

    Strategies for Targeting Tumor Cells

    • Naked antibodies can target tumor cells or be combined with radioactive ligands via streptavidin or bispecific antibodies.
    • Bispecific antibodies can simultaneously bind tumor cells and immune cells, enhancing the immune response.
    • Simple chain variable fragments (scFvs) can be linked to liposomes that deliver drugs or enzymes for localized treatment.
    • Antibody-directed enzyme prodrug therapy (ADEPT) utilizes enzymes to convert prodrugs into active chemotherapeutics at tumor sites.
    • Potelligent technology enhances antibody efficacy by removing fucose, increasing binding affinity to FcγRIIIa (CD16), leading to improved antibody-dependent cellular cytotoxicity (ADCC).

    Clinical Implications and Efficacy

    • Potelligent-enhanced antibodies are expected to show superior efficacy and safety in human patients.
    • Increased Fc receptor binding improves clinical responses and reduces the necessary therapeutic doses.
    • Antibody therapies are typically employed when the patient's immune system is intact, targeting cancer or pathogens.

    Transport and Binding Mechanisms

    • Antibodies travel through fluids, utilizing conventional transport methods and endocytosis (both receptor-mediated and non-receptor-mediated).
    • Specific binding occurs via the Fab portion of the antibody, while non-specific binding occurs through the Fc portion.
    • Antibodies favor binding to soluble antigens; competition exists when antigens are accessible in both soluble and cell-surface forms.

    Antibody Elimination and Stability

    • Antibodies face degradation through proteolysis, with Fc receptors providing protection against rapid catabolism, ensuring longer half-lives.
    • The stability of monoclonal antibodies (mAbs) varies: murine mAbs degrade quickly, while humanized mAbs have a longer lifespan (murine < chimeric < humanized < human).

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    Description

    This quiz covers the various functions of antibodies, including complement-dependent cytotoxicity, neutralization of exotoxins and viruses, prevention of bacterial adherence to host cells, and membrane attack complex formation.

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