• Compare natural/artificial and active/passive immunity.
• Explain how vaccines, herd immunity, and memory cells protect against disease.
• Identify key disease challenges and control strategies.
• Describe what monoclonal antibodies are and how they are made.

Introduction

Immunity protects the body from disease and can be gained in different ways. It may be natural or artificial, and either active (triggering your own immune response) or passive (receiving ready-made antibodies). In today’s interconnected world, understanding how immunity works is essential for managing disease outbreaks and protecting communities.

• Active immunity → Creates memory cells for long-lasting protection.
• Passive immunity → Immediate protection, but no memory.
• Vaccines → Contain inactivated/weakened pathogens or antigenic fragments to stimulate adaptive immunity.

Disease Challenges

• Emerging diseases – Caused by newly identified pathogens, often jumping from animals to humans (zoonoses) or arising from significant genetic changes in existing pathogens (e.g., new influenza strains, SARS-CoV-2). These can spread quickly as populations have little to no pre-existing immunity.
• Re-emerging diseases – Infections that were once under control but are increasing again due to factors like reduced vaccination rates, antimicrobial resistance, or changes in pathogen behaviour (e.g., multi-drug resistant tuberculosis, antibiotic-resistant Staphylococcus aureus).
• Impact on First Nations Australians – Following European colonisation, diseases such as smallpox, influenza, and measles spread rapidly, with devastating mortality rates. These populations had no prior exposure, and therefore no immunity, making the impact especially severe.
• Pathogen evolution – Bacterial resistance and viral antigenic drift/shift create ongoing challenges for treatment and vaccination, as pathogens change to evade drugs or immune detection.

Response Strategies

Scientific approaches

• Rapidly identify the pathogen using microscopy, culture, or molecular tools (e.g., PCR).
• Trace hosts and reservoirs to understand the disease origin.
• Determine mode of transmission (airborne, waterborne, foodborne, vector-borne) to inform targeted control measures.

Social measures

• Quarantine infected individuals to limit spread.
• Hygiene campaigns promoting handwashing, safe food handling, and clean water.
• Contact tracing to find and monitor those exposed to infected individuals.
• Public health messaging to encourage compliance with protective measures.

Vaccination & Herd Immunity

• Vaccines reduce both the severity of disease and its spread.
• Herd immunity occurs when enough people are immune (through vaccination or prior infection) to stop the pathogen circulating widely, protecting vulnerable groups such as newborns or the immunocompromised.

Immunotherapy – Monoclonal Antibodies (mAbs)

Monoclonal antibodies are lab-produced, identical antibodies that bind to one specific antigen on a pathogen, toxin, or cancer cell. They are highly targeted treatments used in medicine and research.

Uses include:

• Treating autoimmune diseases – block overactive immune pathways to reduce inflammation (e.g., rheumatoid arthritis).
• Targeting tumour antigens – attach to markers on cancer cells, helping the immune system destroy them.
• Neutralising pathogens – bind to viruses or bacterial toxins, preventing them from causing harm (e.g., Ebola, COVID-19).

How they are made – Hybridoma Technology:

1. Immunisation – A mouse (or other suitable animal) is injected with the chosen antigen to stimulate B lymphocytes to produce the desired antibody.
2. B cell extraction – B lymphocytes are collected from the animal’s spleen.
3. Cell fusion – These B cells are fused with myeloma (tumour) cells that can divide indefinitely.
4. Hybridoma creation – The fused cells, called hybridomas, have both abilities:

• Make the desired antibody (from the B cell).
• Live and divide forever in culture (from the tumour cell).

1. Screening – Scientists test the hybridomas to find the ones producing the correct antibody.
2. Cloning and culture – The best hybridoma is cloned and grown in large quantities.
3. Purification – The monoclonal antibodies are separated from the culture fluid and purified for use.

These steps produce large batches of identical antibodies, ensuring each molecule binds to the same target with the same strength and specificity.