Proteins on Cell Membranes and Immune Response
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Questions and Answers

What is the mechanism of antibody-dependent cell-mediated cell killing?

  • Decay of C3b and inactivation of the molecule
  • Viral down-regulation of the cytotoxic cell receptor
  • Attachment of the cytotoxic cell to the target cell through MHC class I
  • Engagement of the receptor NKR-P1 with its carbohydrate ligand on the target cell (correct)

    • What is the effect of virally induced down-regulation or alteration of MHC class I on the attachment site?

  • It has no effect on the attachment of cytotoxic cells
  • It increases the expression of NKR-P1 receptors
  • It enhances the attachment of cytotoxic cells
  • It inhibits the attachment of cytotoxic cells (correct)

    • What happens to C3b if a suitable acceptor surface is not found?

  • It becomes active and induces cytotoxicity
  • It remains stable and functional
  • It decays rapidly and becomes inactive (correct)
  • It is up-regulated by viral mechanisms

    • What is the role of the carbohydrate ligand in antibody-dependent cell-mediated cell killing?

    <p>It is recognized by the NKR-P1 receptor</p> Signup and view all the answers

    What is the result of the engagement of the receptor NKR-P1 with its carbohydrate ligand on the target cell?

    <p>Induction of cytotoxicity</p> Signup and view all the answers

    What is the fate of the attachment site if a suitable acceptor surface is not found?

    <p>It is inhibited</p> Signup and view all the answers

    What is the primary function of proteins on cell membranes?

    <p>Block the action of complement</p> Signup and view all the answers

    Which protein initiates the third pathway of complement activation?

    <p>Mannan-binding lectin (MBL)</p> Signup and view all the answers

    What is the result of increasing the rate of breakdown of activated complement components?

    <p>Reduced activation of the complement system</p> Signup and view all the answers

    What is the function of C3b in the complement system?

    <p>Bind to IgG</p> Signup and view all the answers

    What is the final outcome of the complement system?

    <p>Lysis of target cells</p> Signup and view all the answers

    What is the role of mannan-binding lectin in the complement system?

    <p>Initiate the third pathway of complement activation</p> Signup and view all the answers

    What is the function of IgG in the complement system?

    <p>Bind to C3b</p> Signup and view all the answers

    What is the relationship between IgM and IgG in the complement system?

    <p>IgM and IgG are separate pathways in the complement system</p> Signup and view all the answers

    What is the result of C1q activation?

    <p>Sequential binding of C1r and C1s, generating enzyme activity</p> Signup and view all the answers

    What is the function of C4a, C2a, and the vasoactive peptide released from C2?

    <p>They are vasoactive peptides that cause vasodilation</p> Signup and view all the answers

    What is the role of C3 convertase in the classical pathway?

    <p>It cleaves C3 into 'a' and 'b' fragments</p> Signup and view all the answers

    What is the result of the uptake of water by a cell during the lytic pathway?

    <p>Cell swelling and damage</p> Signup and view all the answers

    What is the role of C5a in the classical pathway?

    <p>It is a potent mediator of inflammation</p> Signup and view all the answers

    What is the mechanism of action of NK cells?

    <p>Release of IFN-γ and discharge of granules</p> Signup and view all the answers

    What is the function of the C567 complex?

    <p>It is a potent mediator of inflammation</p> Signup and view all the answers

    What is the significance of ADCC in host defense?

    <p>It is an additional mechanism by which bacteria and viruses can be eliminated</p> Signup and view all the answers

    Which type of T cell recognizes antigens with MHC class II?

    <p>Helper T cells</p> Signup and view all the answers

    What is the function of the CD4 accessory protein?

    <p>To enhance binding and signaling</p> Signup and view all the answers

    Which protein is closely associated with the TCR on the cell surface?

    <p>CD3</p> Signup and view all the answers

    What is the role of the T idiotype?

    <p>Antigen/peptide binding region</p> Signup and view all the answers

    What is the primary function of the variable regions of the alpha and beta chains?

    <p>To make up the T idiotype</p> Signup and view all the answers

    Which type of T cell recognizes antigens with MHC class I?

    <p>Cytotoxic T cells</p> Signup and view all the answers

    What is the result of the increased binding from accessory mechanisms?

    <p>Sufficient reaction with antigen</p> Signup and view all the answers

    What is necessary in addition to recognition of processed antigen to activate T cells?

    <p>Additional signals</p> Signup and view all the answers

    What is the role of perforin in NK cells?

    <p>To create pores in target cell membranes for inducing apoptosis</p> Signup and view all the answers

    Which type of immune response involves the action of perforin in cytolytic T cells?

    <p>Adaptive cellular immunity</p> Signup and view all the answers

    What is the role of lysosomes in phagocytic vacuoles?

    <p>To result in the death of ingested microbes</p> Signup and view all the answers

    What is the role of granzymes in NK cells?

    <p>To induce apoptosis in target cells</p> Signup and view all the answers

    Which type of immune response involves the action of NKT cells?

    <p>Innate cellular immunity</p> Signup and view all the answers

    What is the role of histamine and related vasoactive substances in mast cells?

    <p>To release preformed histamine and related vasoactive substances</p> Signup and view all the answers

    Which of the following is NOT a function of the adaptive immune response?

    <p>Release of preformed histamine and related vasoactive substances</p> Signup and view all the answers

    What is the role of complement components in the innate immune response?

    <p>To opsonize or lyse pathogens</p> Signup and view all the answers

    Which type of immune response involves the production of specific antibodies for opsonization and phagocytosis?

    <p>Adaptive humoral immunity</p> Signup and view all the answers

    What is the role of perforin and granzymes in target cell death?

    <p>Perforin creates pores, and granzymes induce apoptosis</p> Signup and view all the answers

    What is the main function of antibodies secreted by plasma cells?

    <p>To prevent antigens from causing damage in blood and body fluids</p> Signup and view all the answers

    What do MHC molecules provide for T lymphocytes?

    <p>A means of self-recognition and T lymphocyte effector functions</p> Signup and view all the answers

    What type of molecules recognize general patterns of foreignness on non-mammalian cells?

    <p>Detection molecules on innate cells</p> Signup and view all the answers

    What is the primary function of T-cell receptors (TCRs)?

    <p>To recognize specific antigens</p> Signup and view all the answers

    What type of molecules are shared by both the innate and adaptive immune systems?

    <p>Many types of molecules</p> Signup and view all the answers

    What do antigens represent in the immune response?

    <p>Substances recognized by immune components</p> Signup and view all the answers

    What is the main distinction between innate and adaptive immune responses in terms of recognized molecules?

    <p>Innate responses recognize general patterns, while adaptive responses recognize specific antigens</p> Signup and view all the answers

    What is a key function of antibodies on the surface of B cells?

    <p>To recognize specific antigens</p> Signup and view all the answers

    What is the main reason why the term 'allergy' is often misused?

    <p>It is often used loosely to describe any intolerance of environmental factors</p> Signup and view all the answers

    What is the primary function of recognition molecules in the immune system?

    <p>To recognize and respond to antigens</p> Signup and view all the answers

    Which of the following molecules are recognized by the immune system?

    <p>Both pathogens and antigens</p> Signup and view all the answers

    Why is the term 'allergy' often misused in general parlance?

    <p>Because it is often used loosely to describe any intolerance of environmental factors</p> Signup and view all the answers

    What is the significance of recognition molecules in the immune response?

    <p>They recognize and respond to antigens</p> Signup and view all the answers

    What is the role of molecules recognized by the immune system?

    <p>To recognize and respond to antigens</p> Signup and view all the answers

    What is the role of adjuvants in immune response?

    <p>To enhance the immune response to a specific antigen</p> Signup and view all the answers

    How can a single antigenic molecule provoke multiple antibody molecules?

    <p>Each epitope can bind with an individual antibody</p> Signup and view all the answers

    What is the role of detection receptors in phagocytic cells?

    <p>To recognize specific patterns associated with potentially damaging materials</p> Signup and view all the answers

    What is the significance of species differences in immune response?

    <p>They are responsible for genetic factors of the recipient animal</p> Signup and view all the answers

    What is the role of antigenic determinants (epitopes) in immune response?

    <p>They bind with individual antibodies</p> Signup and view all the answers

    What is the result of the activation of the adaptive immune system?

    <p>Inflammation and activation of the adaptive immune system</p> Signup and view all the answers

    What is the role of phagocytic cells in immune response?

    <p>They recognize specific patterns associated with potentially damaging materials</p> Signup and view all the answers

    What is the significance of individual differences in immune response?

    <p>They are a type of genetic factor of the recipient animal</p> Signup and view all the answers

    What is the main function of MHC molecules in the immune response?

    <p>To provide a means of self-recognition</p> Signup and view all the answers

    What type of receptors do T cells have for recognizing antigens?

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

    What is the function of antibodies secreted into blood and body fluids?

    <p>To prevent antigens from causing damage</p> Signup and view all the answers

    What type of molecules recognize general patterns of foreignness on non-mammalian cells?

    <p>Detection molecules</p> Signup and view all the answers

    What is the primary function of antibodies on the surface of B cells?

    <p>To recognize antigens</p> Signup and view all the answers

    What do antigens represent in the immune response?

    <p>Substances that stimulate an immune response</p> Signup and view all the answers

    What is the main distinction between innate and adaptive immune responses in terms of recognized molecules?

    <p>Innate responses recognize general patterns of foreignness, while adaptive responses recognize specific molecules</p> Signup and view all the answers

    What type of molecules are shared by both the innate and adaptive immune systems?

    <p>Many types of molecules</p> Signup and view all the answers

    What is the role of adjuvants in vaccine development?

    <p>To enhance the immune response to a weak antigen</p> Signup and view all the answers

    What is the term for a molecule that interacts with components of the adaptive system?

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

    What is the result of a single antigenic molecule binding with multiple antibody molecules?

    <p>Provocation of many antibody molecules with different binding sites</p> Signup and view all the answers

    What is the function of genetic factors in the recipient animal?

    <p>To provide species and individual differences in immune response</p> Signup and view all the answers

    What is the significance of phagocytic cells recognizing particular patterns associated with potentially damaging materials?

    <p>To lead to inflammation and activation of the adaptive system</p> Signup and view all the answers

    What is an antigenic determinant?

    <p>A region on an antigen molecule that binds to an individual antibody molecule</p> Signup and view all the answers

    What is the relationship between an antigenic molecule and antibody molecules?

    <p>One antigenic molecule can provoke many antibody molecules with different binding sites</p> Signup and view all the answers

    What is the significance of dendritic cell activation?

    <p>To lead to inflammation and activation of the adaptive system</p> Signup and view all the answers

    What is the main reason why the term 'allergy' is often misused?

    <p>It is often used to describe any intolerance of environmental factors.</p> Signup and view all the answers

    What is the primary function of recognition molecules in the immune system?

    <p>To recognize general patterns of foreignness on non-mammalian cells.</p> Signup and view all the answers

    What type of molecules recognize specific antigens on the surface of cells?

    <p>Antibodies.</p> Signup and view all the answers

    What is the primary function of MHC molecules?

    <p>To present antigens to T cells.</p> Signup and view all the answers

    What type of molecules are shared by both the innate and adaptive immune systems?

    <p>Complement components.</p> Signup and view all the answers

    What is the primary function of antibodies on the surface of B cells?

    <p>To recognize specific antigens on the surface of cells.</p> Signup and view all the answers

    What are soluble mediators, which carry messages between cells, known as?

    <p>Cytokines and chemokines</p> Signup and view all the answers

    What is the primary function of cytokines in the immune response?

    <p>To carry messages between cells</p> Signup and view all the answers

    What type of molecule is typically recognized by pattern recognition receptors on dendritic cells?

    <p>Pathogen-associated molecular patterns (PAMPs)</p> Signup and view all the answers

    What is the function of Toll-like receptors in the immune response?

    <p>To recognize and respond to a variety of microbial components</p> Signup and view all the answers

    What is the result of high doses of an antigen?

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

    What is the primary route of entry for an antigen that leads to a response in regional lymph nodes?

    <p>Subcutaneous injection</p> Signup and view all the answers

    What is the result of moderate doses of an antigen?

    <p>Large amounts of antibody with low affinity and broad specificity</p> Signup and view all the answers

    What is the primary site of response for an antigen that enters through inhalation?

    <p>Bronchial lymphoid tissue</p> Signup and view all the answers

    What is the outcome of the engagement of Toll-like receptors on dendritic cells?

    <p>Induction of pro-inflammatory cytokine secretion</p> Signup and view all the answers

    What is the role of Myd88 in Toll-like receptor signaling?

    <p>Adaptor protein</p> Signup and view all the answers

    What is the result of the induction of MAPK kinases in Toll-like receptor signaling?

    <p>Induction of pro-inflammatory cytokine secretion</p> Signup and view all the answers

    What is the function of IRAK enzymes in Toll-like receptor signaling?

    <p>Activation of MAPK kinases</p> Signup and view all the answers

    What is the outcome of the inactivation of IKB in Toll-like receptor signaling?

    <p>Translocation of NFκB</p> Signup and view all the answers

    What is the role of TRAF in Toll-like receptor signaling?

    <p>Adaptor protein</p> Signup and view all the answers

    What is the outcome of the activation of Toll-like receptors on macrophages and neutrophils?

    <p>Activation of pro-inflammatory cytokine secretion</p> Signup and view all the answers

    What is the function of Toll-like receptors?

    <p>Recognition of microbial ligands</p> Signup and view all the answers

    What is the primary function of C5a in the early immune response to virus infection?

    <p>Attracting neutrophils to the site of complement activation</p> Signup and view all the answers

    What is the role of NK cells in the early immune response to virus infection?

    <p>Killing target cells, even in the absence of antibody or antigenic stimulation</p> Signup and view all the answers

    What is the result of C5 convertase activity?

    <p>The initiation of the final lytic pathway</p> Signup and view all the answers

    What is the role of type-I interferons in the early immune response to virus infection?

    <p>Inhibiting the replication of viruses and activating NK cells</p> Signup and view all the answers

    What is the function of IL-12 in the early immune response to virus infection?

    <p>Activating NK cells and promoting the production of type-I interferons</p> Signup and view all the answers

    Which cells are responsible for producing type-I interferons in the early immune response to virus infection?

    <p>Innate immune cells</p> Signup and view all the answers

    What is the role of C3a in the early immune response to virus infection?

    <p>Releasing histamine from mast cells and increasing vascular permeability</p> Signup and view all the answers

    What is the result of the activation of NK cells in the early immune response to virus infection?

    <p>The killing of target cells, even in the absence of antibody or antigenic stimulation</p> Signup and view all the answers

    What is the role of Toll-like receptors (TLRs) in the immune system?

    <p>To induce pro-inflammatory cytokine secretion</p> Signup and view all the answers

    Which protein is involved in the signaling pathway of Toll-like receptors?

    <p>Myd88</p> Signup and view all the answers

    What is the outcome of the activation of Toll-like receptors?

    <p>Pro-inflammatory cytokine secretion</p> Signup and view all the answers

    Which molecule is involved in the inactivation of IKB?

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

    What is the role of IRAK enzymes in the signaling pathway of Toll-like receptors?

    <p>To phosphorylate and activate downstream proteins</p> Signup and view all the answers

    What is the result of the translocation of NFκB?

    <p>Activation of genes in the nucleus</p> Signup and view all the answers

    Which molecule is involved in the induction of MAPK kinases?

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

    What is the outcome of the activation of neutrophils and macrophages by microbial ligands?

    <p>Pro-inflammatory cytokine secretion</p> Signup and view all the answers

    What is the result of C5a activity in complement activation?

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

    What is the role of natural killer cells in the immune response?

    <p>Killing target cells in the absence of antibody</p> Signup and view all the answers

    What type of cytokines are produced by early innate immune cells in response to viral infection?

    <p>Type-I interferons</p> Signup and view all the answers

    What is the role of C5 convertase in the complement system?

    <p>Initiating the lytic pathway</p> Signup and view all the answers

    What is the function of IL-12 in the immune response?

    <p>Activating T cells</p> Signup and view all the answers

    What is the result of the engagement of C3a with mast cells?

    <p>Release of histamine and increased vascular permeability</p> Signup and view all the answers

    What type of cells are involved in the production of type-I interferons in response to viral infection?

    <p>NK cells and early innate immune cells</p> Signup and view all the answers

    What is the role of C5a in the recruitment of neutrophils?

    <p>Attracting neutrophils to the site of complement activation</p> Signup and view all the answers

    What is the primary mechanism of recognition of foreign substances by the innate immune system?

    <p>Recognition of conserved microbial structures through pattern recognition receptors (PRRs)</p> Signup and view all the answers

    What is the name of the molecules that carry messages between cells, influencing the immune response to an antigen?

    <p>Chemokines and cytokines</p> Signup and view all the answers

    What is the result of high doses of an antigen on the immune response?

    <p>Induction of tolerance</p> Signup and view all the answers

    What is the role of Toll-like receptors in the immune response?

    <p>Recognition of conserved microbial structures directly</p> Signup and view all the answers

    What is the outcome of moderate doses of an antigen on the immune response?

    <p>Provocation of large amounts of antibody with mixed affinity and broad specificity</p> Signup and view all the answers

    What is the route of entry for antigens that stimulates the immune response in the bronchial lymphoid tissue?

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

    What is the role of interleukins in the immune response?

    <p>Carrying messages between cells, influencing the immune response to an antigen</p> Signup and view all the answers

    What is the outcome of low doses of an antigen on the immune response?

    <p>Provocation of small amounts of antibody with high affinity and restricted specificity</p> Signup and view all the answers

    What is the primary outcome of the engagement of Toll-like receptors on dendritic cells?

    <p>Induction of MAPK kinases and subsequent activation of genes</p> Signup and view all the answers

    What is the role of Myd88 in Toll-like receptor signalling pathways?

    <p>Adaptor protein for IRAK enzymes</p> Signup and view all the answers

    What is the outcome of the inactivation of IKB in Toll-like receptor signalling pathways?

    <p>Translocation of NFκB</p> Signup and view all the answers

    What is the role of Toll-like receptors in the immune response?

    <p>Recognition of general patterns of foreignness</p> Signup and view all the answers

    What is the result of the activation of IRAK enzymes in Toll-like receptor signalling pathways?

    <p>Induction of MAPK kinases</p> Signup and view all the answers

    What is the role of TRAF in Toll-like receptor signalling pathways?

    <p>TNF receptor-associated factor</p> Signup and view all the answers

    What is the outcome of the translocation of NFκB in Toll-like receptor signalling pathways?

    <p>Activation of genes involved in inflammation</p> Signup and view all the answers

    What is the role of Lipopolysaccharide (LPS) in Toll-like receptor signalling pathways?

    <p>Ligand for Toll-like receptors</p> Signup and view all the answers

    What is the function of Toll-like receptors in the immune system?

    <p>To recognize conserved microbial structures</p> Signup and view all the answers

    What is the role of interleukins, cytokines, and chemokines in the immune response?

    <p>To carry messages between cells</p> Signup and view all the answers

    What is the outcome of high doses of antigen exposure?

    <p>Provoke tolerance</p> Signup and view all the answers

    Which type of molecules recognize general patterns of foreignness on non-mammalian cells?

    <p>Pattern recognition receptors</p> Signup and view all the answers

    What is the primary function of cytokines in the immune response?

    <p>To carry messages between cells</p> Signup and view all the answers

    Which type of cells develop in both the thymus and the bone marrow?

    <p>Natural killer cells</p> Signup and view all the answers

    What is the function of chemokines in the immune response?

    <p>To attract immune cells to the site of infection</p> Signup and view all the answers

    What is the outcome of moderate doses of antigen exposure?

    <p>Provoke mixed affinity and broad specificity</p> Signup and view all the answers

    What is the primary function of C5a in the complement system?

    <p>To attract neutrophils to the site of complement activation</p> Signup and view all the answers

    What type of cells are natural killer cells?

    <p>Large granular lymphocytes</p> Signup and view all the answers

    What cytokines are produced by early innate immune cells in response to viral infection?

    <p>Type-I interferons and IL-12</p> Signup and view all the answers

    Where are natural killer cells primarily found in the body?

    <p>Blood, liver, and secondary lymphoid organs</p> Signup and view all the answers

    What is the role of C3b in the complement system?

    <p>To bind to the initiating complex and promote many biological properties</p> Signup and view all the answers

    What type of immune response involves the production of specific antibodies for opsonization and phagocytosis?

    <p>Adaptive immune response</p> Signup and view all the answers

    What is the result of the engagement of the receptor NKR-P1 with its carbohydrate ligand on the target cell?

    <p>NK cell activation</p> Signup and view all the answers

    What type of molecules recognize general patterns of foreignness on non-mammalian cells?

    <p>Pattern recognition receptors</p> Signup and view all the answers

    What is the outcome of the activation of MAPK kinases in the signaling pathway of Toll-like receptors?

    <p>Induction of pro-inflammatory cytokine secretion</p> Signup and view all the answers

    What is the role of TRAF in the signaling pathway of Toll-like receptors?

    <p>Activation of IRAK enzymes</p> Signup and view all the answers

    What is the outcome of the translocation of NFκB into the nucleus?

    <p>Induction of pro-inflammatory cytokine secretion</p> Signup and view all the answers

    What is the role of IRAK enzymes in the signaling pathway of Toll-like receptors?

    <p>Induction of pro-inflammatory cytokine secretion</p> Signup and view all the answers

    What is the outcome of the activation of Toll-like receptors on dendritic cells?

    <p>Induction of pro-inflammatory cytokine secretion</p> Signup and view all the answers

    What is the role of Myd88 in the signaling pathway of Toll-like receptors?

    <p>Adaptor protein</p> Signup and view all the answers

    What is the outcome of the inactivation of IKB in the signaling pathway of Toll-like receptors?

    <p>Translocation of NFκB into the nucleus</p> Signup and view all the answers

    What is the role of TNF receptor-associated factor (TRAF) in the signaling pathway of Toll-like receptors?

    <p>Activation of IRAK enzymes</p> Signup and view all the answers

    What is the term for soluble mediators that carry messages between cells?

    <p>Cytokines and chemokines</p> Signup and view all the answers

    What type of molecules are recognized by the innate immune system?

    <p>Pathogen-associated molecular patterns (PAMPs)</p> Signup and view all the answers

    What is the function of Toll-like receptors?

    <p>To serve as receptors for a variety of individual bacterial, viral, and fungal components</p> Signup and view all the answers

    What is the result of high doses of an antigen?

    <p>Induction of tolerance</p> Signup and view all the answers

    What is the role of interleukins, cytokines, and chemokines in the immune response?

    <p>To facilitate cell-to-cell communication and coordination</p> Signup and view all the answers

    What is the role of C5a in the immune response?

    <p>To attract neutrophils to the site of complement activation</p> Signup and view all the answers

    What determines the immunogenicity of an antigen?

    <p>The dose and route of entry of the antigen</p> Signup and view all the answers

    What is the primary function of type-I interferons in the immune response?

    <p>To provide early innate immune response to viral infection</p> Signup and view all the answers

    Which of the following cells is responsible for producing IL-12?

    <p>Innate immune cells</p> Signup and view all the answers

    What is the primary function of pattern recognition receptors (PRRs) on dendritic cells?

    <p>To recognize conserved microbial structures</p> Signup and view all the answers

    What is the result of moderate doses of an antigen?

    <p>Production of high-affinity antibodies with broad specificity</p> Signup and view all the answers

    What is the primary function of natural killer cells in the immune response?

    <p>To directly kill infected cells or tumor cells</p> Signup and view all the answers

    What is the role of C3b in the complement system?

    <p>To mark foreign surfaces for destruction by phagocytic cells</p> Signup and view all the answers

    Which of the following cytokines is involved in the activation of natural killer cells?

    <p>IL-12</p> Signup and view all the answers

    What is the primary function of chemokines in the immune response?

    <p>To attract immune cells to the site of infection</p> Signup and view all the answers

    Which of the following cells is primarily responsible for producing cytokines in the immune response?

    <p>Innate immune cells</p> Signup and view all the answers

    Study Notes

    Complement Activation

    • The third pathway of complement activation is initiated by mannan-binding lectin (MBL), a surface receptor that binds to carbohydrates on microbial surfaces.
    • MBL activates C4 and C2, which then split into "a" and "b" fragments, generating enzyme activity (C1 esterase).
    • The complex C4b2b is the classical pathway C3 convertase, which cleaves C3 into active fragments.

    Complement Components

    • C3b is an opsonin that marks pathogens for phagocytosis.
    • C5a and the activated complex C567 are potent mediators of inflammation.
    • C5b initiates the formation of the membrane attack complex (MAC), which forms a hollow, thin-walled cylinder through which salts and water flow, leading to the uptake of water by a cell and its destruction.

    Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)

    • ADCC is an additional mechanism by which bacteria and viruses can be eliminated.
    • ADCC is mediated by engagement of the receptor NKR-P1 with its carbohydrate ligand on the target cell.

    Immune Effector Molecules

    • Humoral immunity: specific antibodies for opsonization and phagocytosis or lysis with complement.
    • Cellular immunity: perforin in NK cells and cytolytic (CD8) T cells creates pores in target cell membranes, allowing entry of granzymes to cause apoptosis.

    T-Cell Receptor (TCR)

    • The TCR is composed of alpha (α) and beta (β) chains, which make up the T idiotype, i.e., the antigen/peptide binding region.
    • The TCR is closely associated with the CD3 protein on the cell surface, which is essential for activation.
    • Recognition of processed antigen alone is not enough to activate T cells; accessory molecules like CD4 and CD8 are required for increased binding and signaling.

    Introduction to Immune System

    • The term "allergy" is often misused to describe any intolerance of environmental factors, regardless of evidence of immunological reactivity to an identified antigen.
    • The normal immune system is the basis for understanding how it can go wrong and cause disease.

    Key Molecules in Immune Response

    • Antibodies recognize specific antigens and are surface receptors of B cells (BCRs).
    • Activated B cells secrete antibodies into blood and body fluids to prevent antigen damage.
    • T cells have structurally similar receptors for recognizing antigens, known as T-cell receptors (TCRs).
    • Major histocompatibility complex (MHC) molecules provide self-recognition and play a fundamental role in T lymphocyte effector functions.

    Innate and Adaptive Immunity

    • Innate immunity recognizes general patterns of 'foreignness' on non-mammalian cells through detection molecules.
    • Adaptive immunity recognizes a wide range of particular molecules or fragments of molecules through specific detection molecules.
    • Innate immunity includes recognition of structures shared by microbes, activation of dendritic cells, and phagocytic cells recognizing particular patterns associated with potentially damaging materials.
    • Adaptive immunity includes recognition of antigens, which are molecules that interact with T- and B-cell recognition receptors and antibodies.

    Antigens and Epitopes

    • Antigens are substances recognized by immune components.
    • An antigenic molecule can have several antigenic determinants (epitopes).
    • Each epitope can bind with an individual antibody, and a single antigenic molecule can provoke many antibody molecules with different binding sites.

    Adjuvants

    • Adjuvants are substances that improve an immune response to a separate, often rather weak, antigen.
    • Adjuvants are used in humans, particularly in vaccines against infective agents and tumours, and are discussed in section 7.3.2.

    Introduction to Immune System

    • Allergy is a misunderstood term, often used loosely to describe any intolerance of environmental factors without objective evidence of immunological reactivity to an identified antigen.

    Key Molecules in Immune Response

    • Antibodies are surface receptors of B cells (BCRs) that recognize specific antigens and are also secreted into blood and body fluids in large quantities to prevent antigen damage.
    • T cells have structurally similar receptors for recognizing antigens, known as T-cell receptors (TCRs).
    • Major histocompatibility complex (MHC) molecules provide a means of self-recognition and play a fundamental role in T lymphocyte effector functions.

    Innate and Adaptive Immunity

    • Innate immunity recognizes general patterns of ‘foreignness’ on non-mammalian cells through detection molecules on innate cells.
    • Adaptive immunity recognizes a wide range of very particular molecules or fragments of molecules through detection molecules on adaptive cells.
    • Antigens are substances that are recognized by immune components.

    Antigen Characteristics

    • An antigenic molecule may have several antigenic determinants (epitopes).
    • Each epitope can bind with an individual antibody.
    • A single antigenic molecule can therefore provoke many antibody molecules with different binding sites.

    Adjuvants

    • Substances that improve an immune response to a separate, often weak, antigen are known as adjuvants.
    • Adjuvants are used in humans, particularly in vaccines against infective agents and tumors.

    Developmental Pathway for Natural Killer Cells

    • The developmental pathway for natural killer (NK) cells is separate from other immune cells because NK cells may develop in both the thymus and the bone marrow.

    Effector Mechanisms and Soluble Mediators

    • Effector mechanisms often depend on messages from initiating or regulating cells.
    • Soluble mediators, which carry messages between cells, are known as interleukins, cytokines, and chemokines.

    Factors Influencing the Immune Response to an Antigen

    • The immune response to an antigen is influenced by factors such as:
      • Nature of the molecule (protein content, size, solubility)
      • Dose (low, moderate, or high)
      • Route of entry (ID, IM, SC, IV, oral, inhalation)

    Molecules Recognized by the Immune System

    • Foreign substances are recognized by both the innate and adaptive systems, but in different ways, using different receptors.
    • The innate system is activated by 'danger signals' due to pattern recognition receptors (PRRs) on dendritic cells recognizing conserved microbial structures directly.
    • Toll-like receptors (TLRs) make up a large family of non-antigen-specific receptors for a variety of individual bacterial, viral, and fungal components.

    Natural Killer Cells

    • NK cells look like large granular lymphocytes and are found in blood, liver, and secondary lymphoid organs, particularly the spleen and mucosal-associated lymphoid tissue (MALT).
    • NK cells can kill target cells, even in the absence of antibody or antigenic stimulation.
    • They play a role in early immune response to viral infection, producing type-I interferons and IL-12, and later, T cell-mediated killing by antigen-specific cells (cytotoxic T cells, CTL).

    Activation of Toll-like Receptors on Dendritic Cells

    • Engagement of Toll-like receptors on dendritic cells leads to the activation of signaling pathways, including TRAF, TNF receptor-associated factor, and IRAK, interleukin-1 receptor-associated kinase.
    • This leads to the induction of pro-inflammatory cytokines and the activation of adaptive immunity.

    Developmental Pathway of NK Cells

    • The developmental pathway for natural killer (NK) cells is thought to occur in both the thymus and the bone marrow.

    Effector Mechanisms and Soluble Mediators

    • Effector mechanisms rely on messages from initiating or regulating cells.
    • Soluble mediators, such as interleukins, cytokines, and chemokines, carry messages between cells.

    Factors Influencing Immune Response

    • Immunogenicity of an antigen is influenced by factors such as:
      • Nature of the molecule (protein content, size, solubility)
      • Dose of the antigen (low, moderate, or high doses affect antibody production)
      • Route of entry (ID, IM, SC, IV, oral, or inhalation routes affect the immune response)

    Recognition of Foreign Substances

    • Both innate and adaptive systems recognize foreign substances, but in different ways.
    • Innate system recognizes foreign substances through:
      • Pattern recognition receptors (PRRs) on dendritic cells.
      • Toll-like receptors (TLRs) recognizing conserved microbial structures.
      • Pathogen-associated molecular patterns (PAMPs).

    Toll-like Receptors

    • Toll-like receptors are a family of non-antigen-specific receptors.
    • They recognize individual bacterial, viral, and fungal components.
    • Examples include recognition of DNA, lipoproteins, and lipopolysaccharides.

    C5a and C3a

    • C5a is an anaphylotoxin that causes histamine release from mast cells.
    • C5a also has chemotactic activity, attracting neutrophils to the site of complement activation.

    Natural Killer Cells

    • NK cells are large granular lymphocytes found in blood, liver, and secondary lymphoid organs.
    • They can kill target cells without antibody or antigenic stimulation.
    • They produce type-I interferons and IL-12 in response to viral infection.

    Role of Cells in Early Immune Response

    • Early immune response involves innate immune cells producing type-I interferons and IL-12.
    • Late immune response involves T cell-mediated killing by antigen-specific cells (CTL).

    Immune Response

    • The developmental pathway for natural killer (NK) cells is separate from other immune cells, as they may develop in both the thymus and the bone marrow.

    Factors Influencing Immune Response

    • The immune response to an antigen is influenced by several factors, including:
      • Nature of the molecule (protein content, size, and solubility)
      • Dose of the antigen (low, moderate, or high)
      • Route of entry of the antigen (ID, IM, SC, IV, oral, or inhalation)

    Molecules Recognized by Immune System

    • Foreign substances are recognized by both the innate and adaptive immune systems, but in different ways, using different receptors.
    • The innate system is activated by 'danger signals' through pattern recognition receptors (PRRs) on dendritic cells, recognizing conserved microbial structures directly, such as:
      • Toll-like receptors (TLRs), a family of non-antigen-specific receptors for various individual bacterial, viral, and fungal components.
      • Pathogen-associated molecular patterns (PAMPs), often repeated polysaccharide molecules.

    Natural Killer Cells

    • NK cells look like large granular lymphocytes and are found in blood, liver, and secondary lymphoid organs, particularly the spleen and mucosal-associated lymphoid tissue (MALT).
    • NK cells can kill target cells, even in the absence of antibody or antigenic stimulation.
    • Early immune response to viral infection involves production of type-I interferons and IL-12 by innate immune cells, followed by T cell-mediated killing by antigen-specific cytotoxic T cells (CTL).

    Complement System

    • C5a, along with C3a, are anaphylotoxins that cause histamine release from mast cells, resulting in increased vascular permeability.
    • C5a also attracts neutrophils to the site of complement activation and has chemotactic activity.
    • The C3b and C4b2b3b complex generates an enzyme, C5 convertase, which initiates the final lytic pathway (the 'attack' sequence).

    Immune Response

    • The developmental pathway for natural killer (NK) cells is separate from other immune cells, as they may develop in both the thymus and the bone marrow.

    Factors Influencing Immune Response

    • The immune response to an antigen is influenced by several factors, including:
      • Nature of the molecule (protein content, size, and solubility)
      • Dose of the antigen (low, moderate, or high)
      • Route of entry of the antigen (ID, IM, SC, IV, oral, or inhalation)

    Molecules Recognized by Immune System

    • Foreign substances are recognized by both the innate and adaptive immune systems, but in different ways, using different receptors.
    • The innate system is activated by 'danger signals' through pattern recognition receptors (PRRs) on dendritic cells, recognizing conserved microbial structures directly, such as:
      • Toll-like receptors (TLRs), a family of non-antigen-specific receptors for various individual bacterial, viral, and fungal components.
      • Pathogen-associated molecular patterns (PAMPs), often repeated polysaccharide molecules.

    Natural Killer Cells

    • NK cells look like large granular lymphocytes and are found in blood, liver, and secondary lymphoid organs, particularly the spleen and mucosal-associated lymphoid tissue (MALT).
    • NK cells can kill target cells, even in the absence of antibody or antigenic stimulation.
    • Early immune response to viral infection involves production of type-I interferons and IL-12 by innate immune cells, followed by T cell-mediated killing by antigen-specific cytotoxic T cells (CTL).

    Complement System

    • C5a, along with C3a, are anaphylotoxins that cause histamine release from mast cells, resulting in increased vascular permeability.
    • C5a also attracts neutrophils to the site of complement activation and has chemotactic activity.
    • The C3b and C4b2b3b complex generates an enzyme, C5 convertase, which initiates the final lytic pathway (the 'attack' sequence).

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    This quiz covers the role of proteins on cell membranes in blocking the binding of antibodies (IgM/IgG) and complement system. It tests your understanding of the immune response and cell membrane function.

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