Immunity Types & Strategies

Introduction to Immunity

• Immunity: The ability of an organism to resist infection by pathogens or the harmful effects of their products.
• Two main types of immunity:
  • Innate Immunity: Non-specific, present from birth.
  • Acquired (Adaptive) Immunity: Specific, develops during an individual’s lifetime.

Acquired Immunity: Natural vs. Artificial

Acquired immunity is further categorized based on how it’s acquired:

• Natural Immunity: Acquired through natural exposure to antigens.
• Artificial Immunity: Acquired through deliberate introduction of antigens or antibodies.

Active vs. Passive Immunity

Acquired immunity can also be classified based on whether the body actively produces antibodies or receives them passively:

• Active Immunity: The body produces its own antibodies in response to an antigen.
• Passive Immunity: The body receives antibodies from an external source.

Types of Acquired Immunity: A Detailed Breakdown

KEY TAKEAWAY: Active immunity involves the body’s own immune response, leading to long-term protection and memory cells, while passive immunity provides temporary protection through borrowed antibodies without memory cell formation.

Active Immunity: In-depth

• Mechanism: Exposure to an antigen triggers the activation of B cells and T cells. B cells differentiate into plasma cells that produce antibodies, and both B and T cells create memory cells.
• Advantages:
  • Long-lasting immunity due to memory cell formation.
  • Provides a more robust and adaptable response upon subsequent exposure to the same antigen.
• Disadvantages:
  • Takes time to develop immunity (days to weeks).
  • May cause mild symptoms of the disease during the initial immune response.

Passive Immunity: In-depth

• Mechanism: Introduction of pre-formed antibodies into the body. These antibodies bind to the antigen and neutralize or eliminate it.
• Advantages:
  • Provides immediate protection.
  • Useful in situations where there is no time for active immunity to develop (e.g., after exposure to a toxin).
• Disadvantages:
  • Temporary protection (weeks to months).
  • No memory cells are produced, so protection is lost once the antibodies degrade.
  • Risk of allergic reactions to the injected antibodies.

Vaccination Programs and Herd Immunity

• Vaccination: A form of artificial active immunity that involves injecting a weakened or inactive form of a pathogen to stimulate an immune response without causing illness.
• Herd Immunity: Occurs when a large proportion of a population is immune to a disease, making the spread of the disease from person to person unlikely.
  • Protects individuals who are not eligible for vaccination (e.g., infants, immunocompromised individuals).
  • Achieved when the vaccination rate is high enough to prevent outbreaks.

EXAM TIP: Be prepared to explain the differences between the four types of acquired immunity (natural active, natural passive, artificial active, and artificial passive) and provide specific examples of each.

Factors Affecting Immunity

• Age: Infants and elderly individuals often have weaker immune systems.
• Nutrition: Malnutrition can impair immune function.
• Stress: Chronic stress can suppress the immune system.
• Underlying Medical Conditions: Certain diseases (e.g., HIV/AIDS) and treatments (e.g., chemotherapy) can weaken the immune system.
• Genetics: Genetic factors can influence an individual’s susceptibility to certain infections.

Emerging and Re-emerging Pathogens

• Emerging Pathogens: Newly identified pathogens or pathogens that are rapidly increasing in incidence or geographic range.
• Re-emerging Pathogens: Pathogens that were previously controlled but are now increasing in incidence.
• Factors Contributing to Emergence and Re-emergence:
  • Globalization: Increased travel and trade can facilitate the spread of pathogens.
  • Climate Change: Altered environmental conditions can favor the spread of certain pathogens.
  • Deforestation and Land Use Changes: Increased contact between humans and wildlife can lead to the transmission of zoonotic diseases.
  • Antimicrobial Resistance: The overuse of antibiotics has led to the emergence of antibiotic-resistant bacteria.
  • Vaccine Hesitancy: Reduced vaccination rates can lead to outbreaks of vaccine-preventable diseases.

COMMON MISTAKE: Students often confuse active and passive immunity. Remember that active immunity requires the body to produce its own antibodies, while passive immunity involves receiving antibodies from an external source.

Strategies to Control Pathogen Spread

• Identification of Pathogen and Host:
  • Rapid diagnostic tests to identify the pathogen causing the infection.
  • Surveillance systems to track the spread of the disease.
• Modes of Transmission:
  • Understanding how the pathogen spreads (e.g., airborne, droplet, contact, vector-borne).
• Measures to Control Transmission:
  • Hygiene practices (e.g., handwashing, sanitation).
  • Quarantine and isolation of infected individuals.
  • Vector control (e.g., mosquito control).
  • Vaccination programs.
  • Public health education.

STUDY HINT: Create a table summarizing the key differences between active and passive immunity, including the mechanism of action, advantages, disadvantages, and examples.

Immunotherapy Strategies

• Immunotherapy: Treatment that uses the body’s own immune system to fight disease.
• Monoclonal Antibodies: Antibodies produced by a single clone of cells, designed to target specific antigens.
  • Treatment of Autoimmune Diseases: Monoclonal antibodies can block the activity of immune cells that are attacking the body’s own tissues.
  • Treatment of Cancer: Monoclonal antibodies can target cancer cells, marking them for destruction by the immune system or delivering toxic drugs directly to the cancer cells.
• Other Immunotherapy Strategies:
  • Checkpoint Inhibitors: Drugs that block proteins that prevent the immune system from attacking cancer cells.
  • CAR-T Cell Therapy: Genetically engineering a patient’s T cells to recognize and attack cancer cells.

APPLICATION: Consider how the principles of active and passive immunity are applied in real-world scenarios, such as vaccination programs and the treatment of infectious diseases.

Impact of European Arrival on Aboriginal and Torres Strait Islander Peoples

• Introduction of new pathogens (e.g., smallpox, measles, influenza) to which Indigenous populations had no prior exposure or immunity.
• Devastating epidemics that resulted in significant population decline and cultural disruption.
• Ongoing health disparities related to infectious diseases in Indigenous communities.

VCAA FOCUS: VCAA often includes questions about the different types of immunity, vaccination programs, and the impact of infectious diseases on populations. Make sure you have a solid understanding of these concepts.