CIE 11.1 Types of Immunity and Vaccination (A-level biology & Osmosis)

Types of Immunity

• Natural Immunity: Develops after infection, resulting from the body’s immune response to antigens.
• Primary Immune Response: When encountering a pathogen for the first time, the body generates memory cells, leading to immunological memory.
• Secondary Immune Response: In a subsequent infection, memory B cells and antibodies quickly eliminate the pathogen.
• Maternal Antibodies: Infants can acquire natural immunity through breastfeeding, where antibodies pass from mother to child.

Artificial Immunity

• Vaccines: Artificial immunity is primarily obtained through vaccinations, which contain dead or weakened viruses.
• Function of Vaccines: Vaccines induce the immune system to create immunological memory against infections, preparing it to respond quickly to live pathogens.
• Virus-Specific: Current vaccines are only designed to combat viruses, not bacterial infections.

Active and Passive Immunity

• Active Immunity: Develops when the body produces its own antibodies in response to exposure to pathogens.
• Vaccination and Active Immunity: Vaccines stimulate active immunity, requiring memory B cells and antibodies for long-lasting protection.
• Booster Shots: Some vaccines may require booster doses over time to maintain immunity due to fading immunological memory.
• Passive Immunity: Comes from antibodies transferred from another animal or a human, providing immediate protection.
• Emergency Treatment: In cases of infection, patients can be treated with injected antibodies for quick immune response support.

Importance of Vaccination

• Development of Immunity: While the immune system can develop natural immunity post-infection, this process typically takes two weeks.
• Rapid Response: Vaccination can prime the immune system for faster responses, often within seven days of exposure.

Herd Immunity

• Concept of Herd Immunity: Achieved when a significant portion of the population is vaccinated, disrupting the chain of pathogen transmission.
• Protection for Vulnerable Populations: Infants and individuals unable to get vaccinated benefit from herd immunity, which protects against outbreaks.
• Risks of Low Vaccination Rates: Decreased vaccination can cause the resurgence of diseases that were nearly eradicated, putting vulnerable populations at risk.

Ethics of Vaccination

• Vaccine Hesitancy Impact: A drop in vaccination rates can jeopardize herd immunity, leading to disease outbreaks.
• Historical Resurgence: Diseases like whooping cough and MMR saw a comeback partly due to vaccination fears, endangering infants.

Antigenic Variability

• Importance of Antigens: Vaccines rely on stable antigens for effective immunity. Changes in antigens can diminish vaccine effectiveness.
• Antigenic Drift vs. Shift: Drift involves minor changes to antigens creating new strains, while shift consists of major changes leading to entirely new viruses.

Influenza Virus Case Study

• Rapid Evolution: Influenza viruses mutate quickly, necessitating new vaccines annually based on prevalent strains.
• Vaccination Participation: Low vaccination rates contribute to the emergence of new strains, complicating control efforts.

Evolutionary Race between Pathogens and Host

• TB Pathogen Characteristics: TB bacteria have a thick cell wall, enabling them to survive inside macrophages, leading to dormant infections.
• HIV Pathogen Characteristics: HIV mutates rapidly, impeding memory cell recognition, and initially targets helper T cells, compromising the immune response.
• Dormancy of HIV: The virus can remain dormant for up to ten years, later reactivating without external reinfection.

Humoral Immunity Overview

• Humoral immunity is a crucial part of the immune system responsible for defending against infections through antibody production.
• Antibodies are specialized proteins produced by B cells, a type of white blood cell, found in blood and body fluids.

Mechanism of Action

• Recognition: B cells identify harmful invaders, such as bacteria or viruses, by detecting specific molecules known as antigens on their surface.
• Activation: Upon recognizing an antigen, B cells become activated, often with assistance from T helper cells. This leads to B cell proliferation and differentiation into plasma cells.

Antibody Production and Function

• Plasma Cells: Once activated, B cells transform into plasma cells, which are responsible for producing and releasing large quantities of antibodies into the bloodstream.
• Neutralization of Pathogens:
  • Antibodies bind to antigens on pathogens, preventing them from infecting host cells.
  • They label pathogens for destruction by other immune cells, such as macrophages.
  • Antibodies can also activate complement proteins, which aid in the destruction of the pathogen.

Administration Routes

• Intramuscularly: Injection deep into muscle tissue.
• Intradermally: Injection into the dermis, the layer beneath the outer skin.
• Intranasally: Delivery through the nasal passages for quicker absorption.
• Subcutaneously: Injection into the layer of fat beneath the skin.
• Orally: Administration via the mouth, allowing gastrointestinal absorption.

Immunoglobulin Response

• Routes of vaccination influence the immunoglobulin produced.
• Intramuscular vaccinations primarily generate IgG antibodies.
• Oral vaccines, such as the rotavirus vaccine, also elicit IgG responses.

Types of Vaccines

• Whole Cell Vaccines: Consist of either live attenuated (weakened) or inactivated (killed) pathogens.
• Fractionated Vaccines: Comprised of subunits or toxoids derived from pathogens.

Inactivated Vaccines

• Pathogens are killed using formalin or heat, preventing disease.
• Induce a humoral (antibody-mediated) immune response but do not foster cellular immunity, resulting in a reduced response.
• Examples include polio, hepatitis A, rabies, and influenza vaccines.

Subunit Vaccines

• Contain immunogenic components from pathogens, such as polysaccharides or proteins.
• Conjugate subunit vaccines combine proteins from different pathogens to enhance immune response.

Polysaccharide Vaccines

• A specific type of subunit vaccine that triggers a T-cell independent response, mainly against protein antigens.
• Less effective in children and pregnant women.
• Associated with the risk of rare complications, such as Guillain-Barré syndrome.