10. Disease and immunity

• What are the three pathogens

  Bacteria, viruses and fungi
• How do pathogens cause disease?

  Damage host cells

  Release toxins
• How are cells recognised as foreign

  They have molecules on their surface called antigens
• What are antigens?

  If foreign non-self protein that stimulates an immune response
• Describe phagocytosis

  Phagocytes recognise and bind to the antigen on the pathogen. the pathogen is engulfed and enclosed in a vesicle lysosomes fuse with the vesicle lysosomes contain lysozymes, which digest the pathogen
• What are lysosomes

  Contain hydrolytic enzymes
• What does the phagocyte do after phagocytosis?

  Places that antigens from the pathogen on its cell surface membrane, becoming an antigen presenting cell
• What is the cellular response?

  Receptors on a specific tea cell recognise and bind the specific antigens. This activates the cell to divide rapidly by mitosis, forming a clone of cells. These cells become cytotoxic, T cells, memory cells and more helper cells.
• What do cytotoxic T cells do?

  Kill infected or abnormal cells.
• What do the T helper cells do?

  Release a chemical called cytokines, which activates B cells
• What is the humoral response?

  BeeCells, either bind with the antigen or activated by cytokines, then divide rapidly by mitosis to form a clone, the cells develop into plasma cells or memory cells.
• What do plasma cells do?

  Produce antibodies.
• What do memory cells do?

  They remain in the blood, and if they encounter the same, antigen, they divide rapidly
• What is antigenic variability?

  The ability of pathogens to change their surface antigens to evade the immune system.
• What are antibodies?


  Proteins that are synthesised by b cells. They react with antigens.
• How many polypeptide chains make up an antibody?

  Four
• What is passive immunity?

  When individuals acquire antibodies from an outside source
• What is active immunity?

  When the immune system is stimulated to produce its own antibodies
• What is natural active immunity?

  Immunity acquired through natural exposure to a pathogen.
• What is artificial active immunity?

  Immunity acquired through vaccination or administration of antibodies.
• What is vaccination?

  The introduction of killed or weakened, pathogens, or isolated antigens to stimulate the production of antibodies
• What makes a vaccination program successful

  Few side effects, easily transported and economically available
• What is herd immunity?

  When it’s not vital to vaccinate 100% of the population in order to stop the spread of disease
• Why is it difficult to completely eradicate disease?

  Some individuals may have a defective immune system. All the pathogen may mutate.
• What are monoclonal antibodies?

  There are antibodies that are produced by the same B-cell, so therefore bind to one specific antigen
• What are monoclonal antibodies used for?

  Medical diagnosis

  Targeted drug treatments

  Pregnancy tests

  Drug testing of athletes
• What is the Eliza test?

  A container is coated with monoclonal antibodies and the sample is added. If the antigen is present, it will bind to the antibodies a second antibody with an enzyme is attached which will then bind into the antigens. A substrate is added. If there is a colour change the antigens were present.
• What is the structure of HIV

  genetic material with reverse transcriptase is enclosed in a capsid. This is surrounded by an envelop with attachment proteins
• How does HIV cause infection

  The attachment proteins bind to specific T cells. The capsid is released into the cell and releases the genetic material and reverse transcriptase. This is used to make a complementary strand of DNA using the viral RNA. This then makes viral DNA and proteins. new viruses bud and infect other cells
• How is HIV treated

  Combination of antiviral drugs