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Questions and Answers
What is the primary function of B cells in the immune system?
What is the primary function of B cells in the immune system?
Which class of immunoglobulin is most abundant in the blood and provides the majority of antibody-based immunity?
Which class of immunoglobulin is most abundant in the blood and provides the majority of antibody-based immunity?
What is an antigen?
What is an antigen?
Which of the following is NOT a type of adaptive immunity?
Which of the following is NOT a type of adaptive immunity?
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What role do memory B cells play in the immune system?
What role do memory B cells play in the immune system?
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What is the primary function of antibodies in the immune response?
What is the primary function of antibodies in the immune response?
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Which immune cells are primarily responsible for cell-mediated immunity?
Which immune cells are primarily responsible for cell-mediated immunity?
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What does the constant region (Fc) of an antibody do?
What does the constant region (Fc) of an antibody do?
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What happens when B cells encounter a T-dependent antigen?
What happens when B cells encounter a T-dependent antigen?
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Which of the following pairs correctly matches a type of immunity with its characteristic?
Which of the following pairs correctly matches a type of immunity with its characteristic?
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How do antibodies facilitate the process of phagocytosis?
How do antibodies facilitate the process of phagocytosis?
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What is the role of antibodies as opsonins?
What is the role of antibodies as opsonins?
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Which of the following accurately describes the structure of antibodies?
Which of the following accurately describes the structure of antibodies?
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What distinguishes the antibody subclasses from one another?
What distinguishes the antibody subclasses from one another?
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What is one way antibodies limit the functions of pathogens?
What is one way antibodies limit the functions of pathogens?
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How do antibodies help in the defense against viruses?
How do antibodies help in the defense against viruses?
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Study Notes
Immunology Lecture 4: Outcomes
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Basic anatomy of the immune system (L1): Covers organs involved in immune function, cells of the immune system, and their basic functions (white blood cells, T and B cells, antigen-presenting cells).
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Immune responses (L2-L6): Includes innate immunity (non-specific immunity), adaptive immunity (cell-mediated and antibody-mediated immunity).
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External defenses (L8): Details about external defenses of the body.
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Immune-related pathology (L7-L8): Discusses different diseases and conditions connected to the immune system, such as cancer, allergies, hypersensitivity, autoimmune disorders, transplant rejection, and HIV.
Adaptive Immunity: Lymphocytes and Antigens
- Antigens: Molecules that trigger a specific immune response.
Lymphocytes and Receptors
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B cells: Have B-cell receptors (BCRs) that bind to specific antigens.
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T cells: Have T-cell receptors (TCRs) that bind to specific antigens.
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Antigens: T-independent (polysaccharides) and T-dependent (proteins).
B Lymphocytes
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B cells differentiate into plasma cells: Produce antibodies.
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Some B cells become memory cells: Remember the pathogen for faster future responses.
B Lymphocytes Produce Antibodies
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B cells differentiate into plasma cells: Secrete antibodies.
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Some B cells become memory cells: Provide immunological memory.
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Antibody classes: Five types of immunoglobulins (Ig): IgG, IgA, IgM, IgE, IgD.
Antibodies
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Structure: Y-shaped proteins with identical antigen-binding sites, variable regions (Fab), and constant regions (Fc).
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Classes (IgM, IgA, IgD, IgG, IgE): Different classes have different functions and locations in the body.
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Biological Functions:
- Neutralization: Block pathogen from entering cells
- Agglutination: Clumping of cells
- Precipitation: Making pathogens insoluble
- Opsonization: Enhanced phagocytosis
- Complement activation: Triggering innate immune response through complement system.
Antibodies: Hinder Pathogens
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Neutralization: Blocking pathogens.
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Agglutination/Precipitation: Making pathogens easier to remove.
Antibodies & Innate Responses: Complement System
- Activation: Antibodies activation or direct activation
- Classical Pathway: Antibody-mediated complement activation following binding to an antibody-antigen complex.
- Alternate Pathway: Direct complement activation to pathogen
Antibodies & Innate Responses: Phagocytosis
- Opsonization: Coating pathogens to enhance phagocytosis.
- Phagocytes (macrophages, neutrophils): Engulf pathogens for elimination.
Antibodies & Innate Responses: NK Cells
- Antibody-dependent cellular cytotoxicity (ADCC): Antibody-coated pathogens triggers NK cell killing.
- NK cells: Kill antibody-coated cells.
Antibody Specificity
- Huge numbers of antigens.
- Each B cell recognizes only one antigen.
- High diversity of antibody responses through genetic shuffling.
Antibody Specificity: Clonal Selection
- Diverse B cells produced, each with a unique antigen receptor.
- Antigen binding causes the specific B cell to be activated.
- Some activated B cells become plasma cells.
- Some activated B cells become memory B cells.
Antibody Specificity: Primary & Secondary Response
- Primary response: Initial antibody production after exposure to antigen.
- Secondary response: Faster and stronger antibody production upon re-exposure to the same antigen due to memory cells.
Antibodies: Active vs Passive Immunity
- Active immunity: Body produces antibodies through exposure.
- Passive immunity: Antibodies borrowed from another source (e.g., breast milk).
- Examples: IgG from mother to fetus, IgA in breast milk, clinically administered antibodies.
Vaccination
- History and development of Louis Pasteur’s vaccine: Attenuated/weakened bacteria to reduce virulence.
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Description
Explore the fundamentals of immunology in Lecture 4, focusing on the anatomy of the immune system, immune responses including innate and adaptive immunity, and immune-related pathology. Understand the roles of lymphocytes and the mechanisms behind antigen recognition and response.
