Infection and response

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• Monoclonal antibodies


  Antibodies made by identical immune cells, clones of the parent cell
• AQA GCSE Biology
• Antibodies


  • Y shaped proteins made by lymphocytes
  • Specific to one binding site on one protein antigen
  • Able to target a specific chemical or specific cells in the body
• Contents


  • 3.1.1 Communicable (Infectious) Diseases
  • 3.1.2 Viral Diseases
  • 3.1.3 Bacterial Diseases
  • 3.1.4 Fungal Diseases
  • 3.1.5 Protist Diseases
  • 3.1.6 Human Defence Systems
  • 3.1.7 Vaccination
  • 3.1.8 Antibiotics & Painkillers
  • 3.1.9 Discovery & Development of Drugs
• Producing monoclonal antibodies


  1. Stimulate mouse lymphocytes to make a particular antibody by exposing them to an antigen

  2. Inject antigen into mouse and combine antibodies with a tumour cell to make clones of the antibody

  3. Combine lymphocytes with a tumour cell to make a hybridoma cell

  4. Single hybridoma cells are cloned, resulting in many divisions, making high quantities of identical cells that all produce the same antibody

  5. Collect and purify large amounts of the antibody
• Pathogens


  Microorganisms that cause infectious disease
• The cells produced in this way create only one type of antibody, hence the name 'monoclonal antibodies'
• Plants can be infected with a range of bacterial and viral pathogens; such as the tobacco mosaic virus (TMV) and rose black spot fungus
• Uses of monoclonal antibodies

  • In pregnancy tests
  • In laboratories to measure levels of hormones, chemicals in blood, or detect pathogens
  • In research to locate or identify specific molecules in a cell or tissue
  • To treat some diseases by binding to cancer cells with a radioactive substance, toxic drug or chemical
• Types of pathogens


  • Viruses
  • Bacteria
  • Protists
  • Fungi
• You are not expected to recall any specific tests or treatments but given appropriate information, you should be able to explain how they work using the principles of antibody specificity
• Plants can also be infested with insects such as aphids
• Bacteria


  • Reproduce rapidly
  • Can affect the host by releasing toxins that damage tissues and make us feel unwell
• Aphids


  Have long sharp mouthpieces that pierce the surface of the stem and into the phloem so that they can feed on the sugar filled sap
• You should be able to describe some of the ways in which monoclonal antibodies can be used in the exam
• Viruses


  • Need a host to survive and reproduce
  • Do not fulfil the 7 life processes, therefore not usually classified as living organisms
  • Do not have nuclei, organelles, or cytoplasm like cells do
• Aphids


  • They can infest a plant in large numbers and remove large quantities of the phloem sap, weakening the plant
  • They can also act as a vector for the transfer of diseases
• Controlling aphid infestation


  1. Biological pest control (using ladybirds, a natural predator of the aphid) to feed on them

  2. Using chemical pesticides
• Viral reproduction


  • Viruses insert their genetic material into host cells and create new protein capsules to build new viral particles
  • Host cell may burst open releasing the viral particles which can go on to infect other cells
• Measles is a highly contagious and a potentially serious viral infectious disease that can be fatal if complications arise
• You should also appreciate the power of monoclonal antibodies and be considerate of ethical issues as a result of their production and use
• The symptoms of plant diseases can apply to more than one disease, which makes identifying them difficult
• Measles is most often seen in children – most young children are vaccinated against it
• Advantages & Disadvantages of monoclonal antibodies

  • Potential to make big improvements to diagnosis and treatment
  • Create more side effects than expected, which has hampered their use
• Identifying plant diseases


  1. Comparing symptoms to those described in gardening manuals or online

  2. Experts visiting the field/woodland to take samples which can then be taken to a lab to undergo DNA analysis

  3. Using testing kits which contain monoclonal antibodies to identify the presence of pathogens quickly and easily
• HIV (Human Immunodeficiency Virus)


  A virus that can eventually lead to Acquired Immunodeficiency Syndrome (AIDS)
• Tobacco mosaic virus (TMV) was the first virus to be isolated by scientists
• Mineral deficiencies


  Plants like all organisms need the correct amount of nutrients to function properly
• TMV is a widespread plant pathogen that infects about 150 species of plants including tomato plants and cucumbers
• Bacterial pathogens produce toxins that cause damage to cells and tissues directly
• In certain optimum conditions, some bacteria can reproduce rapidly (with the fastest being once every 20 minutes for some species of coli)
• Optimum conditions usually involve warmth, moisture and a supply of nutrients
• Salmonella food poisoning is spread by bacteria ingested in food, or on food prepared in unhygienic conditions
• Salmonella is found in the gut of many different animals
• Exam questions about mineral deficiencies may ask you to recommend a fertilizer based on the symptoms that the plant has
• Gonorrhoea is a sexually transmitted disease (STD) – these diseases are also called sexually transmitted infections (STI)
• In 2018 gonorrhoea had the largest increase (26%) of infections in the UK (a total of 56,259 cases!). It was the cause of 13% of diagnosed STDs