Unit 4, Chapter 8: Immunity

Based on the information provided by and the structure of the Edrolo VCE Biology 3-4 Textbook (AI was not used to present any of the information)

Define Active Immunity

Active immunity is protection against a disease created by antibodies and memory cells produced by a person’s own adaptive immune system.

Define Passive Immunity

Passive immunity is protection against a disease created by antibodies from an external source.

Define Natural Immunity

Natural immunity is protection against a disease formed without medical intervention, created by the individuals own immune system or antibodies acquired from a non-medical external source.

Define Natural Active Immunity

Natural active immunity is protection against a disease created by the antibodies and memory cells produced by a person’s own immune system in response to an encountered pathogen, without medical intervention.

Provide an Example of Natural Active Immunity

Contracting a disease from a pathogen (such as chickenpox) and recovering from it through the production of antibodies and gaining immunity through the immunological memory provided by memory cells.

Define Natural Passive Immunity

Natural passive immunity is protection against a disease created by antibodies acquired from a non-medical external source.

Describe 2 Examples of Natural Passive Immunity

• Breastfeeding: human breast milk contains antibodies from the mother’s immune system that are absorbed into the baby’s bloodstream after ingestion.

• Placenta: During pregancy, some of the mother’s antibodies are able to cross the placents and enter the foetus’ bloodstream via the umbilical cord.

Both of these confer the child some protection from pathogens during pregancy or after birth for a short time, helping compensate for babies’ weak adaptive immune systems.

Define Artificial Immunity

Artificial immunity is protection against a disease that has developed as a result of medical intervention, typically through vaccinations or antibody injections.

Define Artificial Active Immunity and Identify an Example

Artificial active immunity is protection against a disease created by antibodies and memory cells produced by a person’s own immune system after a medical intervention. Typically, this is achieved through vaccines.

Define Vaccines

Vaccines are a medical treatment typically containing foreign antigens to stimulate a person’s adaptive immune system, to create immunity to a pathogen without causing the disease.

List 3-5 Potential Primary Components of Vaccines

• Attenuated pathogens (weakened)

• Inactivated pathogens (dead)

• Specific surface proteins from pathogens

• Toxoids (altered toxins that can’t cause disease)

• RNA that enters immune cells causing them to make pathogen-like proteins

Describe the Nature of a Primary Immune Response to a First Vaccine

• After a first vaccination, there is a delay in the adaptive immune system’s response as it takes time for antigen-presenting cells to find T and B cells complementary to the vaccine’s antigen and for the process of clonal selection to occur.

• Eventually a response occurs in which a moderate number of antibodies and memory cells are formed, however these quickly diminish over time.

Describe the Nature of a Secondary Immune Response to a Second Vaccine

• The memory cells created by the first vaccine quickly recognise the antigen in the vaccine and mount a rapid, large immune response.

• This results in the generation of a large number of antibodies and memory cells that go on to create long-lasting immunity.

Explain the Purpose of Vaccination Programs

NOTE: Also known as vaccination schedules

Vaccination programs are often necessary to achieve long-lasting immunity as subsequent vaccinations generate larger, more rapid immune responses.

Define and Outline the Purpose of Booster Vaccines

Booster vaccines are vaccinations given to a person later in time, well after they have completed their initial vaccination program. They aim to enhance existing immunity against a disease by creating new memory cells. This can be necessary as it is normal for T and B cells to die off after a long period of time.

Define Artificial Passive Immunity

Artificial passive immunity is protection against a disease created by antibodies from an external medical source.

Define Antivenom

Antivenom is a medical treatment containing antibodies specific to toxins present in venemous bites or stings, designed to neutralise them.

Explain the Trend in Antibody Concentration in the Graph

Antibody treatments immediately increase the number of antibodies in the blood at the time of the injection. Over time, they degrade until they and the immunity they provided are gone.

NOTE: there is no creation of immunological memory here

Define Herd Immunity

Herd immunity refers to the protection against disease conferred to non-immune individuals when a high percentage of a population is immune to the same disease. This is typically achieved through high vaccintation rates.

Explain How Herd Immunity Works

If sufficiently large proportion of people in a population are immune to a disease via vaccination or natural active immunity, then the disease-causing pathogen cannot easily reproduce and spread through the population.

As a result, non-immune individuals are less likely to come into contact with an infected individual, offering some protection from the disease.

Differentiate Non-Infectious and Infectious Diseases

While non-infectious diseases are illnesses that are not cause by a pathogen (eg. cystic fribrosis), infectious diseases are caused by pathogens (eg. flu, measles - any infection).

Define Contagious Diseases

Contagious diseases are a substet of infectious diseases (pathogen-caused illnesses) that can be transmitted and spread between different people (hosts).

Define Virulence

Virulence is a measure of the potential of a pathogen to cause serious illness or harm. Highly virulent and highly contagious pathogens are of the greatest concern for public health.

Define Emerging Diseases

An emerging disease is an infectious disease that is new to the human population or is rapidly increasing in incidence after historically affecting small isolated populations.

Define Re-Emerging Diseases

A re-emerging disease is an infectious disease that caused major health problems in the past, was previously under control with low incidence but is increasing in incidence enough to become a health problem again for a large number of people.

Identify 6 Factors Contributing the the Emergence and Re-emergence of Diseases

• Evolution of the causative organism

• Globalisation and travel

• Increased exposure of humans to animals

• Increasing human population

• Changing Technology

• Insufficient vaccination of the population

Define a Zoonosis

A zoonosis is an infectious disease that is caused by a pathogen that has transferred from an animal to a human.

Define a Reservoir

A reservior is an environment or animal population in which a pathogen normally lives.

Define a Disease Outbreak

An outbreak is a sudden and unexpected increase in the occurence of a disease in a population.

Define an Epidemic

Epidemics are sudden, widespread increases in the occurence of a disease among a specific population in a specific location at a particular time.

Define a Pandemic

Pandemics occur when a disease spreads to different countries and/or continents in different regions of the world. They typically affect greater numbers of people and are more difficult to control than epidemics.

Define Endemic Diseases

Endemic diseases are diseases that occur at a relatively constant baseline level in a population in a certain location (eg. influenza).

Explain the Effect of Pathogens Introduced by European Colonisation on Indigenous Australians

The arrival of colonisers in land occupied by Indigenous people has historically resulted in the introduction of disease and increase in mortality rates within these populations. Diseases such as smallpox, tuberculosis, influenza and measles caused serious infection and death in Indigenous populations.

Describe 3 Factors Contributing to the Vulnerability of Indigenous Australian Populations

• Lack of immunity: Indigenous populations did not have the immunity against common European diseases that most of the colonisers had. Some diseases such as measles are also more dangerous when first contracted in adulthood.

• Lack of knowledge and experience with European diseases: Although highly knowledgable on the diseases existing in Australia before colonisation, they had no knowledge on the avoidance or treatment of foreign diseases.

• Disruption caused by colonisation: Access to food and water was restricted, and the ability to continue medical practices and their relattionship with culture and Country was disrupted. Camps of Indigenous people also had much higher population densities.

Describe a Physical Method of Identifying Pathogens

• Visualising pathogens using microscopes to determine their structure.

Describe a Phenotypic Method of Identifying Pathogens

• An agar plate designed to allow certain pathogens to grow and multiply, allowing scientists to test for their presence in a sample, identify it and determine courses of treatment/management.

• A series of tests (such as testing if a bacteria is gram positive or negative, anaerobic or aerobic, etc.) can be used to specify a sample’s genus and species

Describe an Immunological Method of Identifying Pathogens

Serology (the study of blood serum) can be used to diagnose disease based on the presence of antibodies or antigens. An example of an experimental technique is ELISA.

Describe a Molecular Method of Identifying Pathogens

Hybridisation-based detection - technique that identifies specific DNA or RNA sequences in a sample by matching them with complementary, labeled strands.

Whole-genome sequencing can be used to provide detailed information about a pathogen.

Identify 5 Modes of Disease Transmission

• Airborne transmission

• Droplet transmission

• Direct physical contact

• Indirect physical contact

• Faecal-oral transmission

Describe Airborne Transmission

The spread of pathogens through air via small particles.

These oarticles can be expelled when a person sneezes, coughs, exhales or talks and stay in the air for prolonged periods of time and can be inhaled after the host has left the vicinity.

Describe Droplet Transmission

Respiratory droplets containing pathogens can remain suspended in the air for a short period of time before falling to the ground or another surface where they can remain within the droplet.

Describe Direct Physical Contact Transmission

The spread of pathogens through contact between a host and another individual. This contact can occur either via skin-to-skin touch, bodily fluids, sexual contact, oral contact and from mother to baby in utero.

Describe Indirect Physical Contact Transmission

The spread of pathogens via contaminated objects or vectors, when there is no direct host-to-host contact (eg. food, water, needles and vector insects such as mosquitoes and ticks).

Describe Faecal-Oral Transmission

Pathogens excreted in faeces can end up being contaminated by another person indirectly, typically by contaminated food and water caused by poor wastewater management, personal hygiene or drinking water.

Differentiate Antiseptics from Disinfectants

While both substances are used to kill or slow the growth of microorganisms, antispetics are applied to living tissue and disinfectants are applied to non-living materials.

Define Antibiotics

Medications used to kill or slow the growth of bacteria. They selectively affect bacterial cells by targeting specific biochemical pathways or components unique to bacteria, without damaging the treated individual’s cells.

Define Antivirals

Medications used to treat viral infections by specifically targeting viruses in a way that interferes with their ability to attach to, replicate in and exit host cells.

Define Fungicides

Medications used to treat fungal infections by specifically targeting fungal cells.

Define Antimicrobial Resistance

The ability of a microorganism to survive exposure to an antimicrobial agent, developed through natural selection. It can occur due to innapropriate use of antibiotics.

Identify 4 Methods of Controlling Disease Transmission

• Quarantine and isolation

• Identification of the pathogen

• Identifying and controlling mode/s of transmission

• Treating infected individuals

Describe the Disease Control Method of Quarantine and Isolation

Once a person has become infected (or could potentially be infected) they may be separated from other healthy people to ensure they do not spread their disease through a community.

Describe the Identification and Control of Mode/s of Transmission

Once a pathogen is identified, mitigation methods can be informed by its known mode/s of transmission. For example, face masks or shields and social distancing was used to control the droplet mode of transmission of COVID-19.

Describe the Disease Control Method of Treating Infected Individuals

Specific curative treatment can be administered to infected individuals and used to target the pathogen. This includes the use of antibiotics, antivirals, and fungicides. Treating the pathogen can eliminate it in infected people and limit the severity spread of disease.

Define Immunotherapy

Immunotherapy is a category of medical treatements that treat diseases by modulating the immune system, typically by either amplifying or reducing an immune response.

Define Activation Immunotherapies

Acitivation immunotherapies aim to induce or amplify immune responses.

Define Suppression Immunotherapies

Suppression immunotherapies aim to prevent or reduce immune responses.

Define Monoclonal Antibodies

Monoclonal antibodies are identical laboratory-made antibodies produced by plasma cell clones and made to target specific antigens. They can be used for immunotherapeutic purposes.

Explain the Process of Producing Monoclonal Antibodies

1. Scientists identify and isolate an antigen that is present on the target cell.

2. An animal (often mice) is vaccinated with the antigen, stimulating an immune response and the selection and proliferation of a corresponding B lymphocyte.

3. The B lymphocytes are extracted from the spleen of the mice.

4. They are then fused with rapidly-dividing cancerous human plasma cells (myeloma) to create hybridoma cells.

5. Hybridomas are screened so that only the cells with the appropriate antibody are selected. These cells are cloned for the mass production of the antibody.

6. Antibodies are then collected and purified before being administered to the patient.

Define Cancer

Cancer is a group of diseases caused by the uncontrolled replication of cells with the ability to migrate to other parts of the body.

Outline How Cancerous Cells Operate

The accumulation of mutations in a cancer cell’s DNA allow it to bypass normal regulatory checkpoints of the cell cycle, giving them survival advantages. Sometimes they are able to evade or suppress the immune system.

Identify and Define the 2 Types of Monoclonal Antibodies

• naked monoclonal antibodies: monoclonal antibodies that do not have any other molecules attached to them

• conjugated monoclonal antibodies: monoclonal antibodies with other molecules attached to them (eg. chemotherapy drugs)

Define Immune Checkpoints

Immune checkpoints are specialised surface proteins on immune cells that, when activated, suppress the immune system. Their primary job is to prevent cells from being overreactive and causing damage to healthy cells as well as helping preventing autoimmunity.

Identify 3 Actions of Monoclonal Antibodies for Activation Immunotherapy

• Antibody-dependent cell-mediated cytotoxicity (ADCC)

• Complement activation

• Checkpoint inhibition

Outline ‘Antibody-Dependent Cell-Mediated Cytoxicity’

• Monoclonal antibodies bind to cancer cells and interact with immune cells (eg. natural killer cells)

• This aids in the recognition of cancer cells as foreign, prompting an immune response targeted at the cancer cells

Outline Complement Activation by Monoclonal Antibodies

• Monoclonal antibodies bind to cancer cells

• They can then interact with complement proteins

• These proteins may kill the cell through the formation of a membrane attack complex or facilitate the actions of other immune cells to destroy the cancer cell

Outline Checkpoint Inhibition by Monoclonal Antibodies

• Immune checkpoints can be stimulated by molecules secreted by some cancer cells, reducing the immune system’s ability to recognise and destroy them.

• Monoclonal antibodies can be used to block immune checkpoints to help prevent this

Compare Immunotherapy with Monoclonal Antibodies to Traditional Cancer Treatments

Traditional cancer treatments (such as radiotherapy and chemotherapy) work by directly targeting and killing cells that are rapidly dividing rather than stimulating the immune system. This causes widespread side effects as healthy cells such as hair follicles and those lining the mouth and gut also divide quickly and are killed by the treatment.

Monoclonal antibodies are much more specific and targeted in their attack, due to their antigen-specific variable regions, with theoretically less widespread side-effects.

Explain the Cause of Autoimmune Disease Symptoms

Autoimmune disease symptoms are brought on by both B and T cells responding to self-tissues as if they were foreign. B cells release autoantibodies (antibodies that target self-cells) and T cells become autoreactive (recognises self-cells as foreign).

Identify 2 Actions of Monoclonal Antibodies for Suppression Immunotherapy

• Cytokine inhibition

• B and T cell depletion and inhibition

Outline Cytokine Inhibition by Monoclonal Antibodies

• Monoclonal antibodies can bind to and inhibit cytokines, reducing the ability of the immune cells to communicate and initiate a response

Outline B and T Cell Depletion and Inhibition by Monoclonal Antibodies

• Monoclonal antibodies that bind to autoreactive T and B cells can be used to inhibit or trigger the destruction of these cells, preventing them from targeting and/or killing self-cells

Compare Immunotherapy with Monoclonal Antibodies to Traditional Cancer Treatments

The majority of autoimmune diseases have no cure at this point in time, and are addressed through symptom management, often by suppressing the whole immune system. This can leave patient’s more susceptible to infections and cancers.

Immunotherapy is a relatively new approach, but would be much more specific in the aspects of the immune system that were suppressed.