Podcast
Questions and Answers
What part of the immunoglobulin structure is responsible for binding to the antigen?
What part of the immunoglobulin structure is responsible for binding to the antigen?
Which immunoglobulin class is the first to be produced during the primary immune response?
Which immunoglobulin class is the first to be produced during the primary immune response?
How many antigen-binding sites does a pentameric IgM have?
How many antigen-binding sites does a pentameric IgM have?
Which of the following statements about the immunoglobulin classes is true?
Which of the following statements about the immunoglobulin classes is true?
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What is the primary characteristic of IgM in comparison to other antibody classes?
What is the primary characteristic of IgM in comparison to other antibody classes?
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What is the primary role of Naïve B cells before activation?
What is the primary role of Naïve B cells before activation?
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What is required for B cell activation to ensure it is not reacting to self?
What is required for B cell activation to ensure it is not reacting to self?
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Which type of B cell actively secretes large amounts of antibodies?
Which type of B cell actively secretes large amounts of antibodies?
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What occurs during the expansion phase of the primary B cell response?
What occurs during the expansion phase of the primary B cell response?
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What process occurs in the germinal center (GC) for activated B cells?
What process occurs in the germinal center (GC) for activated B cells?
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What is the primary role of large aggregates in the bloodstream?
What is the primary role of large aggregates in the bloodstream?
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Which immunoglobulin class is responsible for transporting antibodies across the placenta?
Which immunoglobulin class is responsible for transporting antibodies across the placenta?
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What is the primary function of secretory IgA (sIgA)?
What is the primary function of secretory IgA (sIgA)?
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Which immunoglobulin is predominantly involved in allergic reactions?
Which immunoglobulin is predominantly involved in allergic reactions?
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What percentage of total serum immunoglobulin does IgG represent?
What percentage of total serum immunoglobulin does IgG represent?
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What is the lifespan of IgG antibodies in the serum?
What is the lifespan of IgG antibodies in the serum?
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Which statement about IgD is true?
Which statement about IgD is true?
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What is the primary role of IgA in breast milk?
What is the primary role of IgA in breast milk?
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Which immunoglobulin class is least abundant in serum?
Which immunoglobulin class is least abundant in serum?
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How do basophils and mast cells respond when IgE binds to an antigen?
How do basophils and mast cells respond when IgE binds to an antigen?
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What is the primary purpose of affinity maturation in B cells?
What is the primary purpose of affinity maturation in B cells?
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During class switching, which antibody class do B cells in lymph nodes typically switch to?
During class switching, which antibody class do B cells in lymph nodes typically switch to?
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What occurs to plasma cells when the antigen is no longer present?
What occurs to plasma cells when the antigen is no longer present?
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What characteristic of the secondary immune response distinguishes it from the primary response?
What characteristic of the secondary immune response distinguishes it from the primary response?
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Which process enhances the effectiveness of antibodies during the immune response?
Which process enhances the effectiveness of antibodies during the immune response?
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What is the primary function of antibodies in neutralization?
What is the primary function of antibodies in neutralization?
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How do memory B cells contribute to a stronger immune response upon re-exposure to an antigen?
How do memory B cells contribute to a stronger immune response upon re-exposure to an antigen?
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What role does opsonization play in the immune response?
What role does opsonization play in the immune response?
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Which antibody class is primarily produced by plasma cells that arise from activated B cells in mucosal environments?
Which antibody class is primarily produced by plasma cells that arise from activated B cells in mucosal environments?
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What happens to activated lymphocytes as fewer antigen molecules remain?
What happens to activated lymphocytes as fewer antigen molecules remain?
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What is the primary role of dendritic cells in T cell activation?
What is the primary role of dendritic cells in T cell activation?
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Which statement about central tolerance is correct?
Which statement about central tolerance is correct?
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How do cytotoxic T cells contribute to the immune response?
How do cytotoxic T cells contribute to the immune response?
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What is a key function of regulatory T cells?
What is a key function of regulatory T cells?
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What happens if a T cell's TCR binds an antigen without co-stimulatory molecules?
What happens if a T cell's TCR binds an antigen without co-stimulatory molecules?
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Which type of T cell primarily produces cytokines to activate other immune cells?
Which type of T cell primarily produces cytokines to activate other immune cells?
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What distinguishes peripheral tolerance from central tolerance?
What distinguishes peripheral tolerance from central tolerance?
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What is an antigen?
What is an antigen?
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What are the characteristics of T-dependent antigens?
What are the characteristics of T-dependent antigens?
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What primary organs are responsible for the development of lymphocytes?
What primary organs are responsible for the development of lymphocytes?
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Which type of antigen generally does NOT elicit a strong immune response?
Which type of antigen generally does NOT elicit a strong immune response?
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What role do lymphatic vessels play in the immune system?
What role do lymphatic vessels play in the immune system?
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How does central tolerance contribute to immune function?
How does central tolerance contribute to immune function?
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Which of the following is characteristic of natural killer (NK) cells?
Which of the following is characteristic of natural killer (NK) cells?
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What is the main function of secondary lymphoid organs?
What is the main function of secondary lymphoid organs?
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What triggers an increase in fluid entering the tissues in relation to the immune response?
What triggers an increase in fluid entering the tissues in relation to the immune response?
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Which of the following typically describes T-independent antigens?
Which of the following typically describes T-independent antigens?
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What potential symptoms can result from an immune response?
What potential symptoms can result from an immune response?
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Study Notes
Innate Immunity Barrier
- Mirrors food preservation methods
- Uses methods such as:
- Jarring
- Plastic containers
- Low water content (high salt)
- Acidic pH
- Heat
- Friendly microbes
- Addresses what happens when infectious agents penetrate these barriers
Innate Immunity: Protection Force
- Phagocytic cells
- Complement system
- Defensins
- Cytokines
- Evolved over hundreds of millions of years
- Infectious agents also evolve alongside the immune system
- Rapid evolution of infectious agents
- Recognition of altered self (e.g., cancer cells) without attacking healthy cells is critical
Develop an Array of PRR like receptors – but Rapidly Evolving!
- Recognizes small compounds (especially components of proteins)
- Has a broad range of binding capabilities
- Aims to recognize non-self and attack
- "Not self" identification is a crucial control mechanism
Generating diversity
- Needs a set of starting recognition to avoid infection of the whole population
- Avoid using DNA encoding for recognition due to potential limitations
- Estimate of recognition for 100 million different epitopes
- Does not have space in the genome to encode that many epitopes
Initial Diversity Generated, not Stored.
- Ability to adjust starting recognition to create stronger, more specific responses over time
- Critical balance between immune response and prevention of harm to healthy cells
- Two main branches of the immune system are cellular and humoral
- Mechanisms for generating diversity and recognition are similar in both branches
- Further detail on humoral immunity
- Outlook on cellular immunity
Basic Unit of Immunoglobulin (Ig)
- A Y-shaped protein subunit (monomer) with various named sections
- 2 identical heavy chains
- 2 identical light chains
- The parts can be separated by enzymes
- Antigen-binding fragment (Fab) and Constant fragment (Fc)
- The variable region is at the top of the Fab section (identical on both tips)
There are Five Antibody (Ig) Classes
- IgM, IgG, IgA, IgD, and IgE
- Classes each have unique constant regions, but may sometimes share binding sites
- Each class has distinct functions and properties
- Some classes are multimeric (more than one basic unit)
IgM
- First class produced during primary response, least specific
- Produced in response to some T-independent antigens
- 5% to 13% of circulating antibodies
- Pentameric structure (five monomeric subunits)
- Large size prevents crossing from bloodstream to tissues
- Principally a component of bloodstream infections
- Most effective in initiating classical complement system
IgG
- 80% to 85% of total serum immunoglobulins
- Also exits the bloodstream, entering tissues
- Provides long-term protection (half-life 21 days)
- Most abundant in secondary response
- Effective via neutralization, aggregation, opsonization, complement activation, and antibody-dependent cellular cytotoxicity
- Transported across placenta to fetus's bloodstream
IgA
- Primarily a dimer: secretory IgA (sIgA)
- Important in mucosal immunity (e.g., gastrointestinal, genitourinary, and respiratory tracts)
- Abundant in secretions like saliva, tears, and breast milk
- Protects breastfeed babies from intestinal pathogens
- Primarily neutralizes toxins, viruses, and prevents microbial attachment
- Produced by plasma cells of mucosa-associated lymphoid tissue (MALT)
Other Igs
- IgD (less than 1% of serum immunoglobulins)
- Involved in development and maturation of antibody response
- IgE (barely detectable in serum)
- Primarily bound to basophils and mast cells
- Involved in removing parasitic worms
- Plays a role in allergic reactions (release of histamine and other inflammatory mediators)
Story Line – Creating Initial Diversity
- Haemopoietic stem cells have variable, diversity, and joining region gene segments
- Flexibility in how segments combine through DNA deletions/splicing
Clonal Selection
- Naive B cells display a wide range of "possible affinities" for diverse antigens
- B cell that recognizes the antigen becomes primed and activated
B Cell Activation
- Antigen binding triggers expansion of reactive B cells
- Double-check for self-reaction
B Cell Activation – Expanded
- B cell needs confirmation from a helper T cell before becoming fully active.
- Cell internalizes the antigen, which is then broken down and presented on MHC class II molecules
- Requires T-cell interaction for activation
Generation of Plasma and Memory Cells
- Selected cells expand and differentiate into plasma cells and others form memory cells
- Plasma cells produce antibodies
- Memory cells are long-lived, recognizing the antigen upon further encounters
Affinity Maturation
- Natural selection among proliferating B cells leads to spontaneous mutations
- Mutations lead to improved antigen binding by B-cell receptors
Class Switching
- B cells are initially programmed for IgM production
- Some B cells undergo class switching to different antibody classes (e.g., IgG, IgA) in response to differing environments
- The switching occurs in the lymphoid nodes and mucosal sites
Primary Response Resolution
- Plasma cells undergo apoptosis
- Some B cells become memory B cells that persist for a long time
- Antibody response weakens as antigen is removed
Secondary Response
- Memory cells speed up and enhance the secondary response relative to the primary response
- Secondary response usually clears pathogens before they cause significant harm
Secondary Response Resolution
- Memory B cells quickly react and produce antibodies
- Antibodies are already well-tuned and efficient as a result of affinity maturation
- Future exposures elicit even stronger responses
Roles for Antibodies
- Neutralization, opsonization. complement system activation, immobilization and prevention of adherence, cross-linking, and antibody-dependent cellular cytotoxicity (ADCC)
Antibody roles – illustrated
- Diagram illustrating antibody actions: neutralization opsonization, complement system activation, immobilization and prevention of adherence, antibody dependent cellular cytotoxicity.
Immune Tolerance
- Central tolerance: eliminates immature lymphocytes that recognize self
- Peripheral tolerance: prevents mature lymphocytes from reacting against self or other harmless molecules
Cell Mediated Immunity
- Immune response cannot begin until a lymphocyte becomes activated
- Dendritic cells (DCs) help activate naive T cells
- DCs collect antigens (including from invading microbes) and travel to regions where T cells gather
- Presenting pieces of the antigen, and producing co-stimulatory molecules if the antigen is microbial or represents "danger"
- A T cell can become activated
T-Cell Activation – two paths
- Cytotoxic T cells (CTLs) check infected cell surfaces, induce apoptosis of those with antigen, and generate memory cytotoxic T cells. Helper T cells produce cytokines that activate macrophages, other T cells, and B cells, and promote memory T cells. Additionally, regulatory T cells reduce immune response to prevent overreaction.
What is an antigen?
- Molecules recognized by antibodies, B-cell receptors, or T-cell receptors
- Proteins are generally strong antigens
- Small molecules such as lipids/nucleic acids typically do not function as strong antigens
- T-dependent antigens require help from T helper cells.
Lymphatic system
- A collection of tissues and organs
- Transports lymphocytes to contact with antigens
- Critical for appropriate immune responses
- Lymph flow through lymphatic vessels and lymph nodes.
Primary Lymphoid Organs
- Organs where lymphocytes develop
- Bone marrow (hematopoietic stem cells for blood cell production, B cell maturation) and thymus (T cell maturation).
Secondary Lymphoid Organs
- Lymph nodes, spleen, tonsils, etc.
- Situated throughout the body; include Peyer's patches and mucosal-associated lymphoid tissue (MALT)
- Allow for sampling of intestinal contents and prevention of microbial invasion.
Natural Killer (NK) Cells
- Induce apoptosis in antibody-bound self cells (ADCC)
- Detect infected cells and cause them to self-destruct
- Recognize cells missing MHC (major histocompatibility) markers, some viruses utilize this
"Flu-Like" Symptoms
- Flu-like symptoms such as fever, headache, body aches, cough, sore throat, runny nose, fatigue, nausea, vomiting, and diarrhea.
Summary
- Testing for antibodies against known pathogens; evidence of previous exposure; also blood typing
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Description
Test your knowledge on innate immunity, including its barriers and protective mechanisms. This quiz covers key components such as phagocytic cells, the complement system, and the evolution of infectious agents in relation to the immune system.
