Vaccination and Immunity

Vaccination works by introducing small amounts of dead or inactive pathogens into your body, which might sound scary but it's actually genius! Your white blood cells recognise these harmless intruders and start producing antibodies against them. These white blood cells then divide through mitosis to create copies of themselves.

The really clever bit is that some of these antibody-producing cells stay in your blood for decades. This means if the real pathogen tries to invade your body years later, your immune system can quickly produce antibodies to fight it off before you get ill.

Antibiotic resistance happens when bacteria evolve to survive antibiotic treatment, usually because the antibiotic was overused. This creates resistant strains that are much harder to treat.

Key Point: Herd immunity occurs when enough people are vaccinated to protect even those who aren't vaccinated, as the disease can't spread easily through the population.

Antibiotics and Testing Medicines

Antibiotics are brilliant at killing harmful bacteria without damaging your body cells, but they're completely useless against viruses. This is why your doctor won't give you antibiotics for a cold or flu! Painkillers can help you feel better by reducing symptoms, but they don't actually kill any pathogens.

Medicine testing follows strict stages to ensure safety and effectiveness. Many medicines come from natural sources - digitalis from foxgloves, aspirin from willow trees, and penicillin from mould.

Stage 1 (Preclinical testing) happens on cells, tissues, and live animals because the drug could be toxic to humans. Stage 2 (Clinical testing) involves giving low doses to healthy volunteers first, then finding the optimal dose.

Double blind trials are used where neither patients nor doctors know who receives the real drug or the placebo (fake treatment). This prevents bias from affecting the results.

Remember: It's difficult to create drugs that kill viruses because they live inside our cells, so any treatment might damage healthy tissue too.

Producing Monoclonal Antibodies

Monoclonal antibodies are identical antibodies produced from a single clone of cells, and they're incredibly useful in medicine. The production process is quite clever - scientists inject a lab mouse with an antigen, then collect the antibody-producing lymphocytes from the mouse.

Here's where it gets interesting: lymphocytes don't divide well on their own, so scientists fuse them with tumour cells (which are excellent at dividing). This creates a hybridoma that can both produce antibodies and divide rapidly through mitosis.

Scientists select the hybridoma that produces the specific antibody they want, then allow it to divide and create identical copies. These are the monoclonal antibodies - all specific to one binding site on one protein antigen.

These antibodies have brilliant practical uses. In pregnancy testing, they detect specific hormones produced by the placenta, making tests cheap, easy to use, and highly accurate. They're also essential in lab testing for measuring hormone levels and detecting pathogens in blood samples.

Cool Fact: Each monoclonal antibody is incredibly specific - it will only bind to one particular target, making them perfect for precise medical applications.

Medical Applications and Plant Diseases

Monoclonal antibodies can locate specific molecules in cells by attaching to fluorescent dyes, allowing scientists to see exactly where these molecules are. In cancer treatment, antibodies are made specific to cancer cells and attached to radioactive substances that stop cancer cells growing without harming healthy cells.

Plant diseases can be tricky to identify, but there are clear signs to look for. Tobacco Mosaic Virus is viral, whilst Rose Black Spot is a fungal infection. Look out for discolouration, spots on leaves, stunted growth, decay, and malformed stems or leaves.

Ion deficiencies cause specific problems in plants. Lack of nitrate ions causes stunted growth because nitrates are essential for protein synthesis. Without magnesium ions, plants develop chlorosis (yellowing leaves) because magnesium is needed to make chlorophyll.

When you spot plant diseases, you can identify them using garden manuals, sending samples to labs, or using monoclonal antibody testing kits for quick results.

Heads Up: Cancer treatment with monoclonal antibodies can have very harmful side-effects, even though it's more targeted than traditional treatments.

How Communicable Diseases Spread

Communicable diseases are caused by pathogens - microorganisms like bacteria, viruses, protists, and fungi that can jump from person to person. Understanding how they spread is your first line of defence against getting ill.

Direct contact spreads diseases like athlete's foot through touching infected surfaces. Contaminated water carries diseases like cholera when you drink water contaminated by someone's diarrhoea. Airborne transmission happens when you breathe in tiny droplets from someone coughing or sneezing - this spreads influenza and measles.

Contaminated food is another major route, with salmonella spreading through eating contaminated meat. Some diseases need vectors (carriers) like mosquitoes, which spread malaria protists when they bite.

You can stop the spread through good hygiene (washing hands, cleaning cooking items), killing vectors with insecticides, isolation of infected people, and vaccination programmes.

Smart Strategy: Simple hygiene measures like regular handwashing can prevent most communicable diseases from spreading.

Viral Diseases and How They Work

Viruses aren't actually living cells - they're about 10,000 times smaller than our cells and work like tiny hijackers. Once inside a cell, they use the cell's own machinery to make loads of copies of themselves, then burst the cell open to find new cells to take over.

Measles spreads when infected people cough or sneeze, causing a red rash and high fever. It can be fatal but is rare in the UK because most children are vaccinated. HIV spreads through sexual contact and sharing needles, initially causing flu-like symptoms before weakening the immune system and leading to AIDS.

Tobacco Mosaic Virus (TMV) affects tobacco plants and tomatoes, creating a mosaic pattern on leaves that prevents photosynthesis. This stops plants producing enough sugars for proper growth.

Anti-retroviral drugs can prevent HIV from replicating, meaning people who get early access can live relatively normal lives. However, viruses are much harder to treat than bacterial infections because they hide inside our cells.

Important: Viruses can only reproduce inside living cells, which makes them particularly difficult to treat without damaging healthy tissue.

Viral Disease Examples in Detail

Measles is highly contagious and spreads through coughing and sneezing. You'll recognise it by the distinctive red rash across the body and high fever. Although it can be fatal, it's incredibly rare in the UK thanks to widespread vaccination programmes protecting most children.

HIV (Human Immunodeficiency Virus) spreads through sexual contact and sharing needles or other ways of exchanging bodily fluids. The tricky thing about HIV is that after initial flu-like symptoms (fever, tiredness, aches), people often feel better and think they're fine.

However, HIV gradually weakens the immune system, making people vulnerable to unusual infections and cancers. This stage is called AIDS (Acquired Immune Deficiency Syndrome). The good news is that anti-retroviral drugs can prevent the virus from replicating, allowing people to live normal lives if treatment starts early.

Tobacco Mosaic Virus creates a distinctive mosaic pattern on plant leaves, preventing photosynthesis from working properly. Without enough sugar production, affected plants can't grow normally.

Key Insight: Early treatment makes a massive difference with viral diseases, especially HIV where prompt medical care can prevent progression to AIDS.

Bacterial Infections

Bacteria are single-celled organisms about 100 times smaller than human cells. They can reproduce independently but often thrive in our bodies because of the abundant food supply. The real problem is that they release toxins which damage our cells and tissues.

Salmonella typically spreads through eating contaminated food, especially chicken. You'll know you've got it from fever, stomach cramps, vomiting, and diarrhoea. Most UK chickens are now vaccinated against salmonella, and the infection usually passes by itself within a week.

Gonorrhoea is a sexually transmitted disease causing pain when urinating and thick yellow or green discharge. You can prevent it by avoiding unsafe sex and using barrier methods. Treatment typically involves penicillin, though some resistant strains now need more expensive antibiotics.

The growing problem of antibiotic resistance means some bacterial infections are becoming harder to treat, making prevention more important than ever.

Prevention Tip: Proper food handling and safe sexual practices prevent most bacterial infections, which is much easier than dealing with resistant strains later.