Questions and Answers
Which type of antibody is primarily involved in the response to parasitic infections?
Cytotoxic T cells directly kill infected cells by releasing antibodies.
False
What is the function of cytokines in the immune response?
Cytokines mediate communication between cells and coordinate the immune response.
Th1 cells produce ___________ which enhances anti-viral immunity.
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What must T cells encounter to be activated?
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Match the T cell type with its primary function:
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Which statement best describes Major Histocompatibility Complex (MHC) Class II molecules?
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APCs include dendritic cells, macrophages, and B cells.
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Which type of antibody is primarily responsible for allergic reactions?
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T reg cells promote immune responses against self-antigens.
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Name the four major types of antibodies produced by B cells.
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The process through which B cells recognize antigens and differentiate into plasma cells is known as ______.
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Match the antibody types with their main functions:
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Which cytokine is NOT associated with B cell activation?
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Complement activation is one of the functions of antibodies during pathogen elimination.
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What type of immune response is primarily governed by T cells?
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Th17 cells are associated with ______ inflammatory responses, particularly in chronic infections.
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Which cells are known to help develop immune tolerance to foreign antigens?
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What is the primary function of cytokines like interferon-gamma (IFN-γ) in the innate immune system?
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What type of immunity is primarily involved in eliminating virus-infected cells and cancer cells?
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Cytokines play a significant role in modulating the immune response and mediating communication between cells.
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Basophils and mast cells are both primarily involved in the destruction of parasites.
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Name one example of a Type II hypersensitivity reaction.
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What are the two main classes of adaptive immunity?
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Natural killer (NK) cells release _______ and _______ to induce apoptosis in infected cells.
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The __________ system is activated by antibodies and helps eliminate pathogens through processes like opsonization.
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Match the following types of immunity or reactions with their respective mediators or characteristics:
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Match the immune cells with their primary roles:
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Which cells primarily provide the antibody response in adaptive immunity?
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Adaptive immunity is effective immediately upon infection.
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What are antigen-presenting cells (APCs) commonly involved in?
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Eosinophils play an important role in the destruction of ________ that are too large to be phagocytosed.
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Which of the following cells is a key player in cell-mediated immunity?
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Which antibody is primarily responsible for the secondary immune response?
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IgD has a well-defined function in the immune system.
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What is the role of IgA in the immune system?
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The process by which an activated B cell changes its antibody production is called ______.
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Match the cytokines with their effects on antibody isotype switching:
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Which of the following statements about antibodies is true?
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IgE plays a role in immune response to parasites.
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Which antibody type can cross the placental barrier?
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The antibody that is first expressed during B cell development is ______.
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Which cytokine inhibits the production of IgE?
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What is the primary characteristic of innate immunity?
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Which cell is primarily responsible for the destruction of infected cells through the release of perforins and granzymes?
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Adaptive immunity does not involve T cells.
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Basophils have a longer lifespan compared to mast cells.
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What is the role of antigen-presenting cells (APCs) in the immune response?
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The immune response that primarily targets __________ cells is mediated by cytotoxic T cells.
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What are the types of Antigen Presenting Cells (APCs)?
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Natural killer (NK) cells are an important source of __________, which helps promote antiviral immunity.
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Match the following types of immunity with their characteristics:
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Match the immune cells with their main functions:
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What is the primary function of B cells?
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Which of the following cytokines is primarily produced by ILCs to help regulate immune responses?
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Th17 cells are primarily involved in contingent inflammatory responses related to chronic diseases.
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Adaptive immunity is critical when innate immunity fails to eliminate infectious agents.
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Name the types of T cells associated with regulating immune responses.
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What are the two main classes of adaptive immunity?
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The five major types of antibodies produced by B cells are IgA, IgD, IgE, IgG, and ______.
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What type of immune response do cytotoxic T cells primarily mediate?
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Match the cytokines to their effects on B cell activation:
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The primary function of __________ is to provide immediate defense against infections.
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What is the typical lifespan of a neutrophil in circulation?
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B cells play an essential role in activating T cells.
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Which cells can recognize antigens directly without the need for antigen-presenting cells?
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What are the two main classes of Major Histocompatibility Complex (MHC) proteins?
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Plasma cells are long-lived cells that continue to produce antibodies after the pathogen is eliminated.
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Th1 cells are characterized by the production of __________, which activates macrophages.
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Identify the primary role of IL-17 produced by Th17 cells.
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What is the primary function of helper T (Th) cells?
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B cells arise from _______ stem cells in the bone marrow.
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Match the T cell types with their primary functions:
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Which type of B cell is characterized by having a memory function?
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MHC Class II molecules are found on all nucleated cells.
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What role do dendritic cells play in the adaptive immune response?
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Which antibody is primarily responsible for opsonization during a secondary immune response?
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IgA is primarily involved in the response to mucosal infections.
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What is the primary function of IgE in the immune system?
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The process by which activated B cells change their antibody production is called ______.
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Match the following cytokines with their effect on antibody isotype switching:
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Which antibody can cross the placental barrier?
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Antibodies can eliminate a virus once an infection has occurred.
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Name one antibody type that plays a role in neutralizing toxins.
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The antibody that is first expressed during B cell development is ______.
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Which function is NOT associated with IgD?
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What is the primary role of CD8+ cytotoxic T cells?
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Th cells can directly kill infected cells.
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What activates a T cell?
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MHC Class _____ molecules are found on all nucleated cells.
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Match the T cell types with their functions:
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Which of the following cytokines is primarily released by Th1 cells?
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APCs such as dendritic cells, macrophages, and B cells present exogenous peptides to T cells.
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Name one way that T cells interact with antigen-presenting cells.
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Which type of T cell is primarily associated with the production of IL-17?
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Regulatory T cells (T reg) enhance immune responses against self-antigens.
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What is one primary role of B cells in the immune response?
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Activated B cells can differentiate into __________ or memory B cells.
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Match the following cytokines with their effect on B cell activation:
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What is the main role of Natural Killer (NK) cells in the immune response?
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Which statement best describes the function of plasma cells?
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Mast cells primarily reside in circulation.
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All B cells express the same unique antigen-binding receptor.
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What type of cells are responsible for producing antibodies?
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What type of antibodies can be produced by B cells?
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An imbalance of __________ cytokine production is associated with the development of allergic conditions.
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Eosinophils primarily target __________ that are too large to be phagocytosed.
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What is the primary function of Th2 cells in the immune response?
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Match the following immune cell types with their primary functions:
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Which of the following cytokines is important for promoting antiviral immunity?
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Innate immunity provides specific responses to distinct pathogens.
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What is the lifespan of a neutrophil in circulation?
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Innate lymphoid cells (ILCs) selectively produce __________ to direct immune responses.
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What is the primary function of antigen presenting cells (APCs)?
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Which of the following statements accurately describes cell-mediated immunity?
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Passive immunity is generated through the recipient's own immune response to an antigen.
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Name one type of cell that plays a significant role in adaptive immunity.
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Cell-mediated immunity involves the activation of __________ that can induce apoptosis.
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Match the type of immunity with its characteristics:
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Which antibody is the first to be expressed during B cell development?
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IgD has a well-defined function in the immune system.
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What type of immune response is primarily effective against intracellular pathogens once infection has occurred?
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The process whereby an activated B cell changes its antibody production from IgM to either IgA, IgG, or IgE is known as ______.
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Match the antibody types with their primary functions:
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Which cytokine is known to induce the production of IgA?
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IgG is capable of crossing the placental barrier.
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Which antibody type is primarily responsible for opsonization?
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Antibodies play a crucial role in containing virus proliferation during the ______ phase of infection.
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What is the role of IgE in the immune system?
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Study Notes
Adaptive Immunity Overview
- Adaptive immunity involves specific immune responses against pathogens, primarily mediated by T cells and B cells.
- Antigen-presenting cells (APCs) such as dendritic cells are crucial for the activation of T cells.
T Cells and APCs
- T cells originate from hematopoietic stem cells in the bone marrow and mature in the thymus.
- Each T cell has a unique T-cell receptor (TCR) that recognizes specific antigens.
- T cells require APCs to recognize antigens presented via major histocompatibility complex (MHC) proteins.
MHC Classification
- MHC Class I molecules, present on all nucleated cells, display endogenous peptides.
- MHC Class II molecules, found on specialized immune cells (APCs), present exogenous peptides to T cells.
T Cell Activation
- Activation occurs when T cells encounter an APC displaying the correct peptide-MHC complex.
- TCR engagement triggers cytokine secretion, driving T cell proliferation and differentiation into cytotoxic T cells or T-helper cells.
Cytotoxic T Cells (CD8+)
- CD8+ T cells detect and kill virus-infected or tumor cells via MHC Class I recognition.
- Clonal expansion results in effector cells that induce apoptosis in target cells.
- Memory CD8+ T cells remain post-infection for rapid response to reinfections.
Helper T Cells (CD4+)
- CD4+ T cells enhance immune responses by directing other immune cells.
- They are activated by recognizing antigens presented on MHC Class II molecules.
- Activated Th cells release cytokines to modulate other immune cells' activities.
Th Cell Subtypes
- Th1 cells produce IFN-γ, promoting macrophage bactericidal functions and enhancing anti-viral immunity.
- Th2 cells release IL-4, IL-5, and IL-13, driving IgE antibody production and responses to parasites.
- Th17 cells produce IL-17 cytokines and are involved in chronic inflammation and autoimmune diseases.
Regulatory T Cells (T regs)
- T regs modulate and suppress immune responses to prevent autoimmunity and promote tolerance to self-antigens.
- They play a critical role in resolving immune responses once the threat is cleared.
B Cells and Antibody Production
- B cells develop from hematopoietic stem cells, maturing in the bone marrow with unique surface antibodies.
- They can directly recognize antigens and differentiate into plasma cells, producing antibodies, or memory B cells.
B Cell Differentiation
- Successful antigen binding prompts B cells to proliferate and differentiate into effector or memory cells.
- Plasma cells are short-lived but produce high antibody levels, while memory B cells survive long-term to mount faster responses upon re-exposure.
Types of B Cells
- Innate-like B cells lack memory while adaptive B cells develop memory.
- Various antibody isotypes produced include IgM, IgA, IgG, and IgE, with IgG subclasses differing in functionality.
Antibody-mediated Immunity
- Antibody-mediated immunity relies on B cells producing antibodies that recognize and bind pathogens.
- Once bound, antibodies flag pathogens for destruction through various mechanisms, including phagocytosis and complement activation.
Major Antibody Isotypes
- Five primary antibody classes are involved: IgA, IgD, IgE, IgG, and IgM, each with distinct roles and properties in immune defense.### Innate Immunity: Key Cell Types
- Basophils and mast cells trigger acute inflammatory responses involved in allergies and asthma.
- Mast cells act as immune sentinels and produce cytokines early during infection or injury.
- Basophils are mainly found in circulation, while mast cells reside in connective tissues and mucosal surfaces.
Eosinophils
- Eosinophils are granulocytes with phagocytic capabilities.
- They play a crucial role in targeting and eliminating large parasites.
Natural Killer (NK) Cells
- NK cells reject tumors and destroy virus-infected cells.
- They release perforins and granzymes to induce apoptosis in target cells.
- Produce interferon-gamma (IFN-γ), aiding in the mobilization of antigen-presenting cells (APCs) and enhancing antiviral immunity.
- Involved in the mechanisms associated with allergy and asthma.
Innate Lymphoid Cells (ILCs)
- ILCs are regulatory cells that contribute to innate immunity.
- Different types include ILC-1, ILC-2, and ILC-3.
- Produce cytokines like IL-4, IFN-γ, and IL-17 to direct immune responses and enhance tissue regulation.
Functions and Lifespan of Innate Immune Cells
- Macrophages: Phagocytic; lifespan of months to years; target various pathogens.
- Neutrophils: Short lifespan (hours to days); primarily respond to bacteria and fungi.
- Eosinophils: Live 8–12 days; degranulate and target parasites and allergic tissues.
- Basophils: Die after 1-2 days; involved in allergic reactions through histamine release.
- Mast Cells: Lifespan of months to years; involved in allergic responses and parasite defense.
- Lymphocytes: Varied lifespans (weeks to years); include CD4+ and CD8+ T cells targeting bacteria, viruses, and tumors.
- Natural Killer Cells: Lifespan of 7-10 days; involved in tumor rejection and infected cell destruction.
Adaptive Immunity
- Adaptive immunity strengthens the innate immune response and is essential when innate mechanisms fail.
- Key functions include recognizing non-self antigens, generating specific effector pathways, and developing immunological memory for rapid response against reinfection.
- Forms the basis for effective vaccination strategies.
Stages and Classes of Adaptive Immunity
- Involves several stages: infection, induction, response, and memory development.
- Two main response classes:
- Antibody Response: B cells differentiate into plasma cells to produce antibodies.
- Cell-mediated Response: Antigen-specific T cells activate and proliferate via APC actions.
Antigen Presenting Cells (APCs)
- Major types include dendritic cells, macrophages, and B cells.
- Essential for neutralizing pathogens and eliciting immune responses.
Antibody-Mediated Immunity
- IgM: First antibody type; acts early in response; opsonizes pathogens and fixes complement.
- IgG: Dominant antibody in secondary responses; crosses the placenta; neutralizes toxins and viruses.
- IgA: Protects mucosal surfaces by neutralizing pathogens.
- IgE: Involved in allergic reactions and immune responses against parasites.
Antibody Functions and Isotype Switching
- Class switching allows B cells to switch from producing IgM to IgA, IgG, or IgE based on cytokine influences.
- Key cytokines (IL-4, INF-γ, TGF-β) facilitate or inhibit specific isotype production.
- Antibodies help control virus proliferation in the acute phase, but cell-mediated immunity becomes crucial for established infections.### Adaptive Immunity: Antibody-mediated Immunity
- Cell-mediated immunity protects through antigen-specific cytotoxic T cell activation.
- Key mechanisms include inducing apoptosis in virus-infected or cancerous cells and enhancing macrophage and NK cell activity.
- Cytokine production (e.g., IFNγ) is crucial in mediating immune responses.
Cell-mediated Immunity
- Primarily targets microbes surviving in phagocytes and non-phagocytic infected cells.
- Effective against viruses, intracellular bacteria, fungi, protozoa, and cancers.
- Plays a significant role in transplant rejection.
Passive vs Active Immunity
- Passive immunization transfers active humoral immunity via ready-made antibodies.
- Can occur naturally (maternal antibody transfer) or artificially (exogenous antibody injection).
- Active immunization involves body-produced antibodies after antigen exposure through natural infection or vaccination (attenuated or inactivated pathogens).
- Adjuvants may enhance active immunization efficacy.
Immunopathology
- Defects in the immune response can lead to hypersensitivity, autoimmunity, or immunodeficiency disorders.
Hypersensitivity Reactions
- Four types exist:
- Type I: Immediate hypersensitivity
- Type II: Cytotoxic or antibody-dependent hypersensitivity
- Type III: Immune complex disease
- Type IV: Delayed-type hypersensitivity
Type I Hypersensitivity Reactions
- Most common type involves allergic reactions triggered by specific antigens (allergens).
- Characterized by IgE secretion that sensitizes mast cells, leading to degranulation upon re-exposure.
- Common allergens include pollen, molds, pet dander, and certain foods.
- Treatment includes avoiding triggers, pharmacological interventions (e.g., antihistamines), and in severe cases, epinephrine.
Type II Hypersensitivity Reactions
- Rare reactions developing within 2 to 24 hours; involve IgG and IgM binding to cell-surface molecules.
- Result in complement activation, opsonization, and cell lysis.
- Examples include erythroblastosis fetalis and Goodpasture syndrome.
Type III Hypersensitivity Reactions
- Occur through formation of immune complexes from IgG and IgM binding to soluble proteins.
- Result in tissue deposits, inflammation, and neutrophil influx over days to weeks.
- Treatment typically involves anti-inflammatory agents.
- Examples include systemic lupus erythematosus and serum sickness.
Type IV Hypersensitivity Reactions
- Cell-mediated and antibody-independent reactions taking several days to develop.
- Driven by T cell overstimulation leading to inflammation and tissue damage.
- Resolvable through trigger avoidance and topical corticosteroids; an example is the skin response to poison ivy.
Autoimmunity
- Characterized by immune response against own tissues, featuring self-reactive T cells and autoantibodies.
- Examples of autoimmune diseases include celiac disease, type 1 diabetes, Addison’s disease, and Graves’ disease.
Inflammation
- Unregulated inflammation leads to chronic diseases like rheumatoid arthritis and inflammatory bowel disease.
- Classical symptoms include heat, redness, swelling, and pain; important inflammatory mediators include cytokines and recruited immune cells.
Immunodeficiency
- Immunodeficiency is a state of compromised immune function, either primary (genetic) or secondary (acquired through various factors).
- Hallmark of AIDS, caused by HIV, directly infecting Th cells and compromising the immune response.
Summary of Immunity
- Innate immunity is nonspecific and rapid, involving numerous immune cells and the complement system.
- Adaptive immunity develops with innate responses, producing immunologic memory for faster reactions to previously encountered antigens.
- Integration between innate and adaptive systems promotes effective immune responses; dysfunction in either can lead to immunopathological disorders.
Defining Features of Innate & Adaptive Immunity
- Innate Immunity: Involves various hematopoietic cells (macrophages, neutrophils, etc.), operates immediately, has no immunologic memory, and employs cytokines and complement proteins.
- Adaptive Immunity: Utilizes T and B cells, has a delayed response, benefits from repeated exposures, and primarily relies on antibody production alongside cytokine involvement.
Adaptive Immunity Overview
- Adaptive immunity involves specific immune responses against pathogens, primarily mediated by T cells and B cells.
- Antigen-presenting cells (APCs) such as dendritic cells are crucial for the activation of T cells.
T Cells and APCs
- T cells originate from hematopoietic stem cells in the bone marrow and mature in the thymus.
- Each T cell has a unique T-cell receptor (TCR) that recognizes specific antigens.
- T cells require APCs to recognize antigens presented via major histocompatibility complex (MHC) proteins.
MHC Classification
- MHC Class I molecules, present on all nucleated cells, display endogenous peptides.
- MHC Class II molecules, found on specialized immune cells (APCs), present exogenous peptides to T cells.
T Cell Activation
- Activation occurs when T cells encounter an APC displaying the correct peptide-MHC complex.
- TCR engagement triggers cytokine secretion, driving T cell proliferation and differentiation into cytotoxic T cells or T-helper cells.
Cytotoxic T Cells (CD8+)
- CD8+ T cells detect and kill virus-infected or tumor cells via MHC Class I recognition.
- Clonal expansion results in effector cells that induce apoptosis in target cells.
- Memory CD8+ T cells remain post-infection for rapid response to reinfections.
Helper T Cells (CD4+)
- CD4+ T cells enhance immune responses by directing other immune cells.
- They are activated by recognizing antigens presented on MHC Class II molecules.
- Activated Th cells release cytokines to modulate other immune cells' activities.
Th Cell Subtypes
- Th1 cells produce IFN-γ, promoting macrophage bactericidal functions and enhancing anti-viral immunity.
- Th2 cells release IL-4, IL-5, and IL-13, driving IgE antibody production and responses to parasites.
- Th17 cells produce IL-17 cytokines and are involved in chronic inflammation and autoimmune diseases.
Regulatory T Cells (T regs)
- T regs modulate and suppress immune responses to prevent autoimmunity and promote tolerance to self-antigens.
- They play a critical role in resolving immune responses once the threat is cleared.
B Cells and Antibody Production
- B cells develop from hematopoietic stem cells, maturing in the bone marrow with unique surface antibodies.
- They can directly recognize antigens and differentiate into plasma cells, producing antibodies, or memory B cells.
B Cell Differentiation
- Successful antigen binding prompts B cells to proliferate and differentiate into effector or memory cells.
- Plasma cells are short-lived but produce high antibody levels, while memory B cells survive long-term to mount faster responses upon re-exposure.
Types of B Cells
- Innate-like B cells lack memory while adaptive B cells develop memory.
- Various antibody isotypes produced include IgM, IgA, IgG, and IgE, with IgG subclasses differing in functionality.
Antibody-mediated Immunity
- Antibody-mediated immunity relies on B cells producing antibodies that recognize and bind pathogens.
- Once bound, antibodies flag pathogens for destruction through various mechanisms, including phagocytosis and complement activation.
Major Antibody Isotypes
- Five primary antibody classes are involved: IgA, IgD, IgE, IgG, and IgM, each with distinct roles and properties in immune defense.### Innate Immunity: Key Cell Types
- Basophils and mast cells trigger acute inflammatory responses involved in allergies and asthma.
- Mast cells act as immune sentinels and produce cytokines early during infection or injury.
- Basophils are mainly found in circulation, while mast cells reside in connective tissues and mucosal surfaces.
Eosinophils
- Eosinophils are granulocytes with phagocytic capabilities.
- They play a crucial role in targeting and eliminating large parasites.
Natural Killer (NK) Cells
- NK cells reject tumors and destroy virus-infected cells.
- They release perforins and granzymes to induce apoptosis in target cells.
- Produce interferon-gamma (IFN-γ), aiding in the mobilization of antigen-presenting cells (APCs) and enhancing antiviral immunity.
- Involved in the mechanisms associated with allergy and asthma.
Innate Lymphoid Cells (ILCs)
- ILCs are regulatory cells that contribute to innate immunity.
- Different types include ILC-1, ILC-2, and ILC-3.
- Produce cytokines like IL-4, IFN-γ, and IL-17 to direct immune responses and enhance tissue regulation.
Functions and Lifespan of Innate Immune Cells
- Macrophages: Phagocytic; lifespan of months to years; target various pathogens.
- Neutrophils: Short lifespan (hours to days); primarily respond to bacteria and fungi.
- Eosinophils: Live 8–12 days; degranulate and target parasites and allergic tissues.
- Basophils: Die after 1-2 days; involved in allergic reactions through histamine release.
- Mast Cells: Lifespan of months to years; involved in allergic responses and parasite defense.
- Lymphocytes: Varied lifespans (weeks to years); include CD4+ and CD8+ T cells targeting bacteria, viruses, and tumors.
- Natural Killer Cells: Lifespan of 7-10 days; involved in tumor rejection and infected cell destruction.
Adaptive Immunity
- Adaptive immunity strengthens the innate immune response and is essential when innate mechanisms fail.
- Key functions include recognizing non-self antigens, generating specific effector pathways, and developing immunological memory for rapid response against reinfection.
- Forms the basis for effective vaccination strategies.
Stages and Classes of Adaptive Immunity
- Involves several stages: infection, induction, response, and memory development.
- Two main response classes:
- Antibody Response: B cells differentiate into plasma cells to produce antibodies.
- Cell-mediated Response: Antigen-specific T cells activate and proliferate via APC actions.
Antigen Presenting Cells (APCs)
- Major types include dendritic cells, macrophages, and B cells.
- Essential for neutralizing pathogens and eliciting immune responses.
Antibody-Mediated Immunity
- IgM: First antibody type; acts early in response; opsonizes pathogens and fixes complement.
- IgG: Dominant antibody in secondary responses; crosses the placenta; neutralizes toxins and viruses.
- IgA: Protects mucosal surfaces by neutralizing pathogens.
- IgE: Involved in allergic reactions and immune responses against parasites.
Antibody Functions and Isotype Switching
- Class switching allows B cells to switch from producing IgM to IgA, IgG, or IgE based on cytokine influences.
- Key cytokines (IL-4, INF-γ, TGF-β) facilitate or inhibit specific isotype production.
- Antibodies help control virus proliferation in the acute phase, but cell-mediated immunity becomes crucial for established infections.### Adaptive Immunity: Antibody-mediated Immunity
- Cell-mediated immunity protects through antigen-specific cytotoxic T cell activation.
- Key mechanisms include inducing apoptosis in virus-infected or cancerous cells and enhancing macrophage and NK cell activity.
- Cytokine production (e.g., IFNγ) is crucial in mediating immune responses.
Cell-mediated Immunity
- Primarily targets microbes surviving in phagocytes and non-phagocytic infected cells.
- Effective against viruses, intracellular bacteria, fungi, protozoa, and cancers.
- Plays a significant role in transplant rejection.
Passive vs Active Immunity
- Passive immunization transfers active humoral immunity via ready-made antibodies.
- Can occur naturally (maternal antibody transfer) or artificially (exogenous antibody injection).
- Active immunization involves body-produced antibodies after antigen exposure through natural infection or vaccination (attenuated or inactivated pathogens).
- Adjuvants may enhance active immunization efficacy.
Immunopathology
- Defects in the immune response can lead to hypersensitivity, autoimmunity, or immunodeficiency disorders.
Hypersensitivity Reactions
- Four types exist:
- Type I: Immediate hypersensitivity
- Type II: Cytotoxic or antibody-dependent hypersensitivity
- Type III: Immune complex disease
- Type IV: Delayed-type hypersensitivity
Type I Hypersensitivity Reactions
- Most common type involves allergic reactions triggered by specific antigens (allergens).
- Characterized by IgE secretion that sensitizes mast cells, leading to degranulation upon re-exposure.
- Common allergens include pollen, molds, pet dander, and certain foods.
- Treatment includes avoiding triggers, pharmacological interventions (e.g., antihistamines), and in severe cases, epinephrine.
Type II Hypersensitivity Reactions
- Rare reactions developing within 2 to 24 hours; involve IgG and IgM binding to cell-surface molecules.
- Result in complement activation, opsonization, and cell lysis.
- Examples include erythroblastosis fetalis and Goodpasture syndrome.
Type III Hypersensitivity Reactions
- Occur through formation of immune complexes from IgG and IgM binding to soluble proteins.
- Result in tissue deposits, inflammation, and neutrophil influx over days to weeks.
- Treatment typically involves anti-inflammatory agents.
- Examples include systemic lupus erythematosus and serum sickness.
Type IV Hypersensitivity Reactions
- Cell-mediated and antibody-independent reactions taking several days to develop.
- Driven by T cell overstimulation leading to inflammation and tissue damage.
- Resolvable through trigger avoidance and topical corticosteroids; an example is the skin response to poison ivy.
Autoimmunity
- Characterized by immune response against own tissues, featuring self-reactive T cells and autoantibodies.
- Examples of autoimmune diseases include celiac disease, type 1 diabetes, Addison’s disease, and Graves’ disease.
Inflammation
- Unregulated inflammation leads to chronic diseases like rheumatoid arthritis and inflammatory bowel disease.
- Classical symptoms include heat, redness, swelling, and pain; important inflammatory mediators include cytokines and recruited immune cells.
Immunodeficiency
- Immunodeficiency is a state of compromised immune function, either primary (genetic) or secondary (acquired through various factors).
- Hallmark of AIDS, caused by HIV, directly infecting Th cells and compromising the immune response.
Summary of Immunity
- Innate immunity is nonspecific and rapid, involving numerous immune cells and the complement system.
- Adaptive immunity develops with innate responses, producing immunologic memory for faster reactions to previously encountered antigens.
- Integration between innate and adaptive systems promotes effective immune responses; dysfunction in either can lead to immunopathological disorders.
Defining Features of Innate & Adaptive Immunity
- Innate Immunity: Involves various hematopoietic cells (macrophages, neutrophils, etc.), operates immediately, has no immunologic memory, and employs cytokines and complement proteins.
- Adaptive Immunity: Utilizes T and B cells, has a delayed response, benefits from repeated exposures, and primarily relies on antibody production alongside cytokine involvement.
Adaptive Immunity Overview
- Adaptive immunity involves specific immune responses against pathogens, primarily mediated by T cells and B cells.
- Antigen-presenting cells (APCs) such as dendritic cells are crucial for the activation of T cells.
T Cells and APCs
- T cells originate from hematopoietic stem cells in the bone marrow and mature in the thymus.
- Each T cell has a unique T-cell receptor (TCR) that recognizes specific antigens.
- T cells require APCs to recognize antigens presented via major histocompatibility complex (MHC) proteins.
MHC Classification
- MHC Class I molecules, present on all nucleated cells, display endogenous peptides.
- MHC Class II molecules, found on specialized immune cells (APCs), present exogenous peptides to T cells.
T Cell Activation
- Activation occurs when T cells encounter an APC displaying the correct peptide-MHC complex.
- TCR engagement triggers cytokine secretion, driving T cell proliferation and differentiation into cytotoxic T cells or T-helper cells.
Cytotoxic T Cells (CD8+)
- CD8+ T cells detect and kill virus-infected or tumor cells via MHC Class I recognition.
- Clonal expansion results in effector cells that induce apoptosis in target cells.
- Memory CD8+ T cells remain post-infection for rapid response to reinfections.
Helper T Cells (CD4+)
- CD4+ T cells enhance immune responses by directing other immune cells.
- They are activated by recognizing antigens presented on MHC Class II molecules.
- Activated Th cells release cytokines to modulate other immune cells' activities.
Th Cell Subtypes
- Th1 cells produce IFN-γ, promoting macrophage bactericidal functions and enhancing anti-viral immunity.
- Th2 cells release IL-4, IL-5, and IL-13, driving IgE antibody production and responses to parasites.
- Th17 cells produce IL-17 cytokines and are involved in chronic inflammation and autoimmune diseases.
Regulatory T Cells (T regs)
- T regs modulate and suppress immune responses to prevent autoimmunity and promote tolerance to self-antigens.
- They play a critical role in resolving immune responses once the threat is cleared.
B Cells and Antibody Production
- B cells develop from hematopoietic stem cells, maturing in the bone marrow with unique surface antibodies.
- They can directly recognize antigens and differentiate into plasma cells, producing antibodies, or memory B cells.
B Cell Differentiation
- Successful antigen binding prompts B cells to proliferate and differentiate into effector or memory cells.
- Plasma cells are short-lived but produce high antibody levels, while memory B cells survive long-term to mount faster responses upon re-exposure.
Types of B Cells
- Innate-like B cells lack memory while adaptive B cells develop memory.
- Various antibody isotypes produced include IgM, IgA, IgG, and IgE, with IgG subclasses differing in functionality.
Antibody-mediated Immunity
- Antibody-mediated immunity relies on B cells producing antibodies that recognize and bind pathogens.
- Once bound, antibodies flag pathogens for destruction through various mechanisms, including phagocytosis and complement activation.
Major Antibody Isotypes
- Five primary antibody classes are involved: IgA, IgD, IgE, IgG, and IgM, each with distinct roles and properties in immune defense.### Innate Immunity: Key Cell Types
- Basophils and mast cells trigger acute inflammatory responses involved in allergies and asthma.
- Mast cells act as immune sentinels and produce cytokines early during infection or injury.
- Basophils are mainly found in circulation, while mast cells reside in connective tissues and mucosal surfaces.
Eosinophils
- Eosinophils are granulocytes with phagocytic capabilities.
- They play a crucial role in targeting and eliminating large parasites.
Natural Killer (NK) Cells
- NK cells reject tumors and destroy virus-infected cells.
- They release perforins and granzymes to induce apoptosis in target cells.
- Produce interferon-gamma (IFN-γ), aiding in the mobilization of antigen-presenting cells (APCs) and enhancing antiviral immunity.
- Involved in the mechanisms associated with allergy and asthma.
Innate Lymphoid Cells (ILCs)
- ILCs are regulatory cells that contribute to innate immunity.
- Different types include ILC-1, ILC-2, and ILC-3.
- Produce cytokines like IL-4, IFN-γ, and IL-17 to direct immune responses and enhance tissue regulation.
Functions and Lifespan of Innate Immune Cells
- Macrophages: Phagocytic; lifespan of months to years; target various pathogens.
- Neutrophils: Short lifespan (hours to days); primarily respond to bacteria and fungi.
- Eosinophils: Live 8–12 days; degranulate and target parasites and allergic tissues.
- Basophils: Die after 1-2 days; involved in allergic reactions through histamine release.
- Mast Cells: Lifespan of months to years; involved in allergic responses and parasite defense.
- Lymphocytes: Varied lifespans (weeks to years); include CD4+ and CD8+ T cells targeting bacteria, viruses, and tumors.
- Natural Killer Cells: Lifespan of 7-10 days; involved in tumor rejection and infected cell destruction.
Adaptive Immunity
- Adaptive immunity strengthens the innate immune response and is essential when innate mechanisms fail.
- Key functions include recognizing non-self antigens, generating specific effector pathways, and developing immunological memory for rapid response against reinfection.
- Forms the basis for effective vaccination strategies.
Stages and Classes of Adaptive Immunity
- Involves several stages: infection, induction, response, and memory development.
- Two main response classes:
- Antibody Response: B cells differentiate into plasma cells to produce antibodies.
- Cell-mediated Response: Antigen-specific T cells activate and proliferate via APC actions.
Antigen Presenting Cells (APCs)
- Major types include dendritic cells, macrophages, and B cells.
- Essential for neutralizing pathogens and eliciting immune responses.
Antibody-Mediated Immunity
- IgM: First antibody type; acts early in response; opsonizes pathogens and fixes complement.
- IgG: Dominant antibody in secondary responses; crosses the placenta; neutralizes toxins and viruses.
- IgA: Protects mucosal surfaces by neutralizing pathogens.
- IgE: Involved in allergic reactions and immune responses against parasites.
Antibody Functions and Isotype Switching
- Class switching allows B cells to switch from producing IgM to IgA, IgG, or IgE based on cytokine influences.
- Key cytokines (IL-4, INF-γ, TGF-β) facilitate or inhibit specific isotype production.
- Antibodies help control virus proliferation in the acute phase, but cell-mediated immunity becomes crucial for established infections.### Adaptive Immunity: Antibody-mediated Immunity
- Cell-mediated immunity protects through antigen-specific cytotoxic T cell activation.
- Key mechanisms include inducing apoptosis in virus-infected or cancerous cells and enhancing macrophage and NK cell activity.
- Cytokine production (e.g., IFNγ) is crucial in mediating immune responses.
Cell-mediated Immunity
- Primarily targets microbes surviving in phagocytes and non-phagocytic infected cells.
- Effective against viruses, intracellular bacteria, fungi, protozoa, and cancers.
- Plays a significant role in transplant rejection.
Passive vs Active Immunity
- Passive immunization transfers active humoral immunity via ready-made antibodies.
- Can occur naturally (maternal antibody transfer) or artificially (exogenous antibody injection).
- Active immunization involves body-produced antibodies after antigen exposure through natural infection or vaccination (attenuated or inactivated pathogens).
- Adjuvants may enhance active immunization efficacy.
Immunopathology
- Defects in the immune response can lead to hypersensitivity, autoimmunity, or immunodeficiency disorders.
Hypersensitivity Reactions
- Four types exist:
- Type I: Immediate hypersensitivity
- Type II: Cytotoxic or antibody-dependent hypersensitivity
- Type III: Immune complex disease
- Type IV: Delayed-type hypersensitivity
Type I Hypersensitivity Reactions
- Most common type involves allergic reactions triggered by specific antigens (allergens).
- Characterized by IgE secretion that sensitizes mast cells, leading to degranulation upon re-exposure.
- Common allergens include pollen, molds, pet dander, and certain foods.
- Treatment includes avoiding triggers, pharmacological interventions (e.g., antihistamines), and in severe cases, epinephrine.
Type II Hypersensitivity Reactions
- Rare reactions developing within 2 to 24 hours; involve IgG and IgM binding to cell-surface molecules.
- Result in complement activation, opsonization, and cell lysis.
- Examples include erythroblastosis fetalis and Goodpasture syndrome.
Type III Hypersensitivity Reactions
- Occur through formation of immune complexes from IgG and IgM binding to soluble proteins.
- Result in tissue deposits, inflammation, and neutrophil influx over days to weeks.
- Treatment typically involves anti-inflammatory agents.
- Examples include systemic lupus erythematosus and serum sickness.
Type IV Hypersensitivity Reactions
- Cell-mediated and antibody-independent reactions taking several days to develop.
- Driven by T cell overstimulation leading to inflammation and tissue damage.
- Resolvable through trigger avoidance and topical corticosteroids; an example is the skin response to poison ivy.
Autoimmunity
- Characterized by immune response against own tissues, featuring self-reactive T cells and autoantibodies.
- Examples of autoimmune diseases include celiac disease, type 1 diabetes, Addison’s disease, and Graves’ disease.
Inflammation
- Unregulated inflammation leads to chronic diseases like rheumatoid arthritis and inflammatory bowel disease.
- Classical symptoms include heat, redness, swelling, and pain; important inflammatory mediators include cytokines and recruited immune cells.
Immunodeficiency
- Immunodeficiency is a state of compromised immune function, either primary (genetic) or secondary (acquired through various factors).
- Hallmark of AIDS, caused by HIV, directly infecting Th cells and compromising the immune response.
Summary of Immunity
- Innate immunity is nonspecific and rapid, involving numerous immune cells and the complement system.
- Adaptive immunity develops with innate responses, producing immunologic memory for faster reactions to previously encountered antigens.
- Integration between innate and adaptive systems promotes effective immune responses; dysfunction in either can lead to immunopathological disorders.
Defining Features of Innate & Adaptive Immunity
- Innate Immunity: Involves various hematopoietic cells (macrophages, neutrophils, etc.), operates immediately, has no immunologic memory, and employs cytokines and complement proteins.
- Adaptive Immunity: Utilizes T and B cells, has a delayed response, benefits from repeated exposures, and primarily relies on antibody production alongside cytokine involvement.
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Description
This quiz focuses on the key concepts of adaptive immunity, highlighting the roles of cytotoxic T cells and B cells. Participants will learn how these immune cells interact with viral antigens and the mechanisms they use to neutralize infections. Test your knowledge about the adaptive immune response and its components.
