B2 Keeping Healthy

1. B2 Keeping Healthy Lesson 2: Defending against Disease

2. Objectives • MUST describe how the immune system responds to pathogens • SHOULD explain the roles of white blood cells in the immune system • COULD understand how the body responds to pathogens it has encountered before

3. Key Words • You need to be able to define the following: • Immune system • White blood cell • Antibody • Antigen • Memory cell • Immune

5. Textbook Answers 1) Skin, saliva, stomach acid, tears, healing of wounds, immune system. 2) One type engulfs microorganisms and digests them; another type produces specific antibodies that bind to specific antigens on the microorganisms and inactivate them so that they can be destroyed. 3) Students draw an antibody with an active site the same shape as antigen 1 in Figure 2 on page 43 of the Student Book. 4) Because the shapes fit together like a key fits in a lock. 5) They ensure a rapid response to pathogens that have been encountered before, and mean that an illness does not need to be suffered twice. 6) Your immune system has memory cells to respond rapidly to the invasion of that disease. Some diseases or illnesses you cannot become immune to because they are able to mutate and have different antigens that are not recognised by the memory cells.