infection and response

• Diet and amount of exercise


  Can cause Type I diabetes
• Diet and amount of exercise

  Can cause cardiovascular disease
• Alcohol


  Causes impaired liver function, impaired brain function, affected development of unborn babies
• Smoking


  Causes lung disease and cancers, affected development of unborn babies
• Cancer


  The result of changes in cells that lead to uncontrolled growth and division by mitosis
• Rapid division of abnormal cells


  Can form a tumour
• Malignant tumours


  Cancerous tumours that invade neighbouring tissues and spread to other parts of the body in the blood, forming secondary tumours
• Benign tumours


  Non-cancerous tumours that do not spread around the body
• Monoclonal antibodies


  Identical copies of one type of antibody
• Production of monoclonal antibodies

  1. Mouse is vaccinated to produce one population of antibodies

  2. Spleen cells that form antibodies are collected from the mouse

  3. These are fused with tumour cells called myeloma cells to form hybridoma cells

  4. These are grown in a laboratory and those that produce the desired antibodies are selected

  5. Antibodies are collected
• Vaccines


  Put a dead or inactivated form of the disease to stimulate the white blood cells to produce the antibodies needed
• Vaccination process


  1. Vaccine is injected

  2. White blood cells recognise the antigens on the pathogen

  3. White blood cells produce antibodies that destroy the pathogen

  4. Some white blood cells are left behind as memory cells

  5. If re-infected, the memory cells will remember the antigens and produce antibodies quickly to destroy the pathogen before illness occurs
• Pre-clinical trials


  Very low doses of the drug are given to healthy volunteers to see if the group is safe and effective
• Clinical trials


  Larger numbers of healthy volunteers and patients receive the drug to find the optimum dose
• Peer review


  The results of clinical trials will be assessed and checked by independent researchers
• Double-blind trials


  Neither the patient nor the doctors know who has been given the real drug and who has been given the placebo (no effect) to reduce bias
• Non-specific defences in the human body

  1. Nose: Nasal hairs, sticky mucus and cilia prevent pathogens entering through the nostrils

  2. Trachea and bronchus: Lined with mucus to trap dust and pathogens, cilia move the mucus upwards to be swallowed

  3. Stomach acid: Kills most ingested pathogens

  4. Skin: Hard to penetrate waterproof barrier, glands secrete oil which kill microbes
• Lymphocytes


  Fight pathogens
• T cells


  Produce antibodies that bind to the toxins produced by pathogens, neutralising them
• Phagocytes


  Are attracted to sites of infection, surround the pathogen and engulf it, enzymes digest and destroy the pathogen
• Antibodies


  Produced by lymphocytes, bind to antigens on the pathogen's surface to help destroy it
• Phagocytes fight pathogens
• Communicable diseases


  Caused by pathogens, most commonly viruses, bacteria, fungi and protozoa
• Ways communicable diseases can be transmitted


  • Direct contact
  • Water
  • Air
  • Preparation and ingestion of unhygienic food
• Ways to prevent or reduce transmission of pathogens

  • Sterilising water
  • Suitable personal hygiene
  • Vaccination
  • Contraception
• Methods to control communicable diseases


  • Hygiene - hand washing, disinfecting surfaces and machinery, covering mouth when coughing
  • Isolation - isolating infected individuals
  • Controlling vectors - destroying or controlling the population of the vector that spreads the disease
  • Vaccination - protecting large numbers of individuals against diseases
• Salmonella


  Causes fever, cramps, vomiting, diarrhoea, transmitted through food prepared in unhygienic conditions or not cooked properly, controlled by improving food hygiene, washing hands, vaccinating poultry, cooking food thoroughly
• Gonorrhoea


  Causes green discharge from penis or vagina, transmitted through sexual contact or exchange of bodily fluids, controlled by using condoms and treatment with antibiotics
• Signs of plant disease

  • Stunted growth
  • Spots on leaves
  • Areas of decay
  • Abnormal growth
  • Discolouration of leaves
  • Presence of pests
• Physical defences in plants


  Thick waxy cuticle, cellulose cell walls, physical barriers against infection
• Chemical defences in plants


  Some plants produce antibacterial chemicals, limiting the space for pathogens to grow
• Mechanical defences in plants


  Thorns, spines, and poisons protect plants from damage and herbivores
• Malaria


  Causes recurrent fever, transmitted by mosquitoes, controlled by preventing mosquito breeding and using mosquito nets
• Rose black spot


  Causes purple/black spots on leaves, transmitted by wind or water, controlled by removing infected leaves and spraying with fungicide
• Measles


  Causes fever and red skin rash, transmitted by droplet infection from sneezes and coughs, controlled by vaccination
• HIV


  Initially causes flu-like symptoms, seriously damages the immune system, transmitted through sexual contact and exchange of bodily fluids, controlled by antiretroviral drugs and use of condoms
• Tobacco mosaic virus


  Causes mosaic pattern on leaves, transmitted through wounds in the plant epidermis, controlled by removing infected leaves and controlling pests that damage the leaves
• Specific bacteria need to be treated by specific antibiotics
• Antibiotics have greatly reduced deaths from infectious bacterial diseases, but antibiotic-resistant strains of bacteria are emerging
• Treating viral diseases


  • Antibiotics do not affect viruses
  • Drugs that kill viruses often damage the body's tissues
  • Painkillers treat the symptoms of viral diseases but do not kill pathogens