Chapter 11: Specific Resistance To Infection

Question 1

• What is a lymphocyte?
• What are specific defences?
• There are 2 parts to the immune response. One part the humeral response and the other, cell-mediated immunity. Explain each.
• What are B cells?
• What are T cells?
• What are antigens?

Answer 1

• A type of white blood cell found in the lymph nodes and associated with the immune system.
• Defences of the body that are directed against specific pathogens.
• Humeral response is a response triggered by foreign substances entering the body. Cell-mediated immunity involves formation of special lymphocytes that destroy invading agents.
• Type of lymphocyte that develops in plasma cells that produce antibodies or memory cell.
• Type of lymphocyte that can differentiate into different kinds of cells to fight against pathogens.
• Substances that cause a specific immune response to produce antibodies against it.

Question 2

• What is an anti-body?
• Explain how anti-bodies are specific.
• What happens when an antigen activates B-cells?
• What is the primary response?
• Why is the body’s immune system slow at first?

Answer 2

• A substance produced in response to a specific antigen that it combines with to destroy.
• They combine with specific antigens with specific active sites similar to the lock and key model to form antigen-antibody complex.
• The B-cells enlarge and divide into clones. Most of the clones become plasma cells secreting antibodies for the antigens. These antibodies circulate in the blood, lymph and extracellular fluid to reach the site of the invasion of micro-organisms. The rest of the B-cells remain as memory cells to allow the future responses occurring faster.
• Immune reaction to first exposure to an antigen.
• It takes days to build up large amounts of antibodies as it takes time for B-cells to multiply and differentiate into plasma cells.

Question 3

• When the same antigen attacks, the ‘secondary response’ occurs. Why is the immune responses so fast compared to the first time?
• Outline 6 ways in which antibodies produced by plasma cells can fight a pathogenic infection.
• What is cell-mediated immunity?
• In cell-mediated immunity, what happens when a foreign antigen enters the body?

Answer 3

• With the 2nd response, plasma cells are able to form very quickly so antibody levels in the blood plasma rises quickly.
  1. Combine with antigens inhibiting reactions with other cells (virus)
  2. Bind to surface of antigen preventing them entering cells (Virus) 3.Coat antigens to enhance phagocytosis (bacteria)
  4. Causes antigens to agglutinate enhancing phagocytosis (bacteria)
  5. Dissolve them
  6. React with soluble substances to make them insoluble and thus enhancing phagocytosis (bacteria)
• Resistance to the intracellular phase of bacterial and viral infections
• T-cells for that antigen become activated and divide into clones, some remain in the lymphoid tissue as memory cells. The rest develop into either killer T-cells, Helper T-cells or Suppressor T-cells.

Question 4

• What are killer T-Cells?
• What are Helper T-Cells?
• What are Suppressor T-Cells?
• Explain the humeral response in 5 steps
• What is immunity?
• Define vaccination

Answer 4

• A type of T-cell that kills antigens by attaching to them and secreting a substance to destroy it.
• A type of T-cell that takes part in the humeral response and anti-body mediated immunity. They bind to antigens, secrete cytokines at infection site to activate more B lymphocytes and intensifies macrophage activity.
• A type of T-cell that release substances that inhibit T- and B-cell activity once infection has been dealt with.
  1. Antigen reaches lymphoid tissue.
  2. Certain B-cells are stimulated to undergo rapid cell division.
  3. Most new B-cells develop into plasma cells, which produce antibodies and release them into blood and lymph.
  4. Antibodies combine with the antigens to destroy them.
  5. Some of the new B-cells form memory cells.
• Resistance to infection from invading micro-organisms.
• The artificial introduction of antigens to a person so that they aquire immunity without suffering from the illness.

Question 5

• Explain cell-mediated immunity in 5 steps
• Explain the difference between artificial and natural immunity.
• What is passive immunity?
• What is active immunity?
• Name 3 parts of the body that produces fluids with a low pH. Also how does this low pH affect invading micro-organisms?
• Why is mucosa considered to be an external barrier to pathogens?
• Distinguish between communicable disease, contagious disease and non-communicable disease.

Answer 5

1. Antigen reaches lymphoid tissue.
2. T-cells are stimulated to undergo rapid cell division.
3. Most new T-cells develop into killer T-cells or helper T-cells
4. Killer T-cells destroy the antigen, while helper T-cells intensifies macrophage activity.
5. Some sensitised T-cells form memory cells.
   -Natural immunity occurs without human intervention whereas artificial immunity is produced by giving a person an antigen, which triggers the immune response.
   -Immunity produced by the introduction of antibodies from another person. It is short term, lasts only until antibodies are broken down.
   -Immunity produced by the body manufacturing antibodies against foreign antigens.
   -Stomach, vagina and skin. Low pH means it’s acidic so kills micro-organisms.
   -Separates digestive cavity from blood and internal organs. To reach these micro-organisms must first pass through this barrier
   -Communicable disease: any disease that can be spread from one person to another.
   Contagious: Easily passed from one person to another by direct or indirect contact.
   Non-communicable: Cannot be passed from one person to another.

Question 6

• What are the 4 types of vaccines.
• What are 2 ethical concerns on vaccines?
• What are antibiotics?
• Explain the following 2 types of antibiotics: bactericidal antibiotics and bacteriostatic antibiotics.
• What problems are involved with organ transplants?
• Are viruses living cells? Why or why not?
• Viruses are described as ‘obligate parasites’ why?

Answer 6

• Living attenuated micro-organisms, dead micro-organisms, toxoids and sub-units.
• Some people are concerned about treatment of animals in production of vaccines and morals are questioned for people who are opposed to the way in which original cells of vaccines were derived from human foetuses.
• Chemical that kills bacteria.
• Bactericidal antibiotics kill bacteria by changing the structure of the cell wall/membrane or by disrupting the action of essential enzymes. Bacteriostatic antibiotics stop bacteria from reproducing by disrupting protein synthesis.
• The new organ is recognised as foreign causing an immune response. Patients therefore need to take immunosuppressant drugs to prevent rejection of the kidney but this can reduce immune response to other antigens increasing risk of disease.
• No, they don’t follow the 7 life processes (MRSGREN): move, respire, sensitivity, grow, reproduce, excrete and nutrition.
• They require a living host cell to reproduce by reprogramming the DNA or RNA of the host cell you make more virus particles.

Question 7

• What are antiviral drugs?
• Describe phagocytosis. Which type of white blood cell is actively engaged in it?
• What is the lymphatic system’s role in defending the body against disease?
• What’s the difference between an antibiotic and an antiviral drug?
• Why are both antibiotic and antiviral drugs usually considered an internal protection?
• What is adaptive immunity?
• What are plasma cells?
• What are differences between T and B lymphocytes?

Answer 7

• Drugs used to kill viruses.
• Phagocytosis is the ingestion of pathogens by cells. It is the major function of macrophages.
• Helps to protect the body against spread of disease by removing bacteria from lymph. Lymphocytes carry out immune responses which are specific defence mechanisms
• Antibiotics are produced by fungi or plants designed to kill bacteria. Antiviral drugs are unable to kill the virus but they stop it from spreading and reduce its symptoms.
• They pass through external barriers and work from the inside of your body.
• Immunity that develops after exposure to pathogens by recognising it as foreign. Can be acquired actively or passively.
• B lymphocytes that produce antibodies.
• T cells are long lived, mature in thymus and responsible for cell mediated immunity. Whereas B cells are short lived, mature in bone marrow and responsible for humeral response.