Immunology Lecture 4 Quiz

Immunology Lecture 4 Outcomes

• Basic anatomy of the immune system (L1):

  • Organs involved in immune function
  • Cells of the immune system and their basic functions
    • Basic white blood cell functions
    • T and B cell-specific functions
    • Antigen-presenting cells

• Immune responses (L2-L6):

  • Innate immunity
    • Non-specific immunity
  • Adaptive immunity
    • Cell-mediated immunity
    • Antibody-mediated immunity

• External defenses (L8):

  • (Not detailed, only listed)

• Immune-related pathology (L7-L8):

  • Cancer
  • Allergy
  • Hypersensitivity
  • Auto-immune disorders
  • Transplant rejection
  • HIV

Adaptive Immunity: Lymphocytes & Antigens

• Antigen: Molecule triggering a specific immune response.

Lymphocytes & Receptors

• B cells: Have B-cell receptors (BCRs) that bind specific antigens.
• T cells: Have T-cell receptors (TCRs) that bind specific antigens.
• Antigens: T-independent (polysaccharides) or T-dependent (proteins)

B Lymphocytes

• Differentiation: B cells differentiate into plasma cells.
• Function: Produce antibodies.
• Memory cells: Some B cells become memory cells for a faster response in future exposures.

B Lymphocytes Produce Antibodies

• Plasma cells: Produce antibodies.
• Memory cells: Some B cells become memory cells for future faster responses.
• Antibody classes: Five types of immunoglobulins (Ig): IgG, IgA, IgM, IgE, IgD.

Antibodies

• Structure: Y-shaped proteins with two identical antigen-binding fragments (Fab).
• Function: Identify and neutralize pathogens.
• Classes:
  • IgM: Important in primary immune responses.
  • IgA: Found in mucosal secretions (saliva, milk).
  • IgG: Most abundant antibody; crosses the placenta.
  • IgE: Involved in allergic reactions.
  • IgD: Functions as a B-cell receptor.
• Locations: Attached to B cells; free in plasma; secreted by plasma cells.

Antibodies: Hinder Invaders/Pathogens

• Neutralization: Prevents pathogens from entering host cells.
• Agglutination: Clumping pathogens, making them easier for phagocytes to engulf.
• Precipitation: Forms insoluble complexes that are easily removed.

Antibodies & Innate Responses: Complement System

• Activation: Initiated by antibodies binding to pathogens.
• Membrane attack complex: Forms pores in pathogens, leading to lysis.

Antibodies & Innate Responses: Phagocytosis

• Opsonization: Antibodies tagging pathogens for phagocytic cells.
• Phagocytes: Engulf pathogens (e.g., macrophages, neutrophils).

Antibodies & Innate Responses: NK Cells

• Antibody-dependent cellular cytotoxicity (ADCC): NK cells recognize and kill antibody-coated pathogens.

Antibody Specificity

• Diversity: Huge number of different foreign molecules.
• Specificity: Each B cell responds to only one antigen.
• Clonal selection: B cells with the correct receptor proliferate and differentiate into plasma cells.

Antibody Specificity: Primary & Secondary Responses

• Primary response: First exposure to an antigen, slower response.
• Secondary response: Second exposure to the same antigen, faster and more potent response.

Antibodies: Active vs Passive Immunity

• Active immunity: Production of antibodies through exposure.
• Passive immunity: "Borrowed" immunity; antibodies from another source.

Vaccination

• Louis Pasteur: Developed the anthrax vaccine.
• Mechanism: Attenuated/weakened bacteria to reduce virulence.