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| Question | Answer |
| What is an immune response? | An immune response is the body's reaction to a foreign antigen (molecules found on the surfaces of cells). This involves specific (antigen-specific) and non-specific responses |
| What are the 4 stages of an immune response? | 1. Phagocytosis 2. T lymphocyte activation 3. B lymphocyte activation and plasma cell production 4. Antibody production |
| Outline the process of phagocytosis | 1. A phagocyte recognises antigens on a pathogen 2. The phagocyte engulfs the pathogen. This is made easier by opsonins 3. The pathogen is now contained in a phagosome. A lysosome fuses with the phagosome. The enzymes break down the pathogen 4. The phagocyte presents the pathogen's antigens to activate other immune system cells' it acts as an antigen-presenting cell |
| What is a phagocyte? | Type of white blood cell that carries out phagocytosis |
| What are opsonins? | Molecules in the blood that attaches to foreign antigens to aid phagocytosis) |
| What is a phagosome? | A type of vesicle |
| What do lysosomes contain? | Digestive enzymes |
| What is a T lymphocyte? | A type of white blood cell covered with receptors |
| What do the receptors of T lymphocytes bind to? | The receptors on T lymphocytes bind to antigens presented by antigen-presenting cells (APC) |
| Complete the sentences: Each T lymphocyte has a different ____________ on its surface. When the receptor on the surface of a T lymphocyte meets a _______________ antigen, it binds to it - so each T lymphocyte will bind to a different ________. This process _________ the T lymphocyte and is known as _________ ___________. The activated T lymphocyte then undergoes _________ __________ - it divides to produce clones of itself. | Each T lymphocyte has a different RECEPTOR on its surface. When the receptor on the surface of a T lymphocyte meets a COMPLIMENTARY antigen, it binds to it - so each T lymphocyte will bind to a different ANTIGEN. This process ACTIVATES the T lymphocyte and is known as CLONAL SELECTION. The activated T lymphocyte then undergoes CLONAL EXPANSION - it divides to produce clones of itself. |
| Name the 3 types of T lymphocytes | T helper cells T killer cells T regulatory cells |
| What is the role of T helper cells? | Release substances to activate B lymphocytes and T killer cells |
| What is the role of T killer cells? | Attach to and kill cells that are infected with a virus |
| What is the role of T regulatory cells? | Suppress the immune response from other white blood cells. This helps to stop immune system cells from mistakenly attacking the host's body cells |
| TRUE OR FALSE: Some activated T lymphocytes become memory cells | TRUE |
| What are B lymphocytes covered with? | B lymphocytes are covered with antibodies. Each B lymphocyte has a different shaped antibody on its membrane, so different ones bind to different shaped antigens |
| What are antibodies? | Proteins that bind to antigens to form an antigen-antibody complex |
| Outline clonal selection and clonal expansion of B lymphocytes | CLONAL SELECTION: When the antibody on the surface of a B lymphocyte meets a complementary antigen, it bind to it - so each B lymphocyte will bind to a different antigen. This, together with substances released from helper T cells, activates the B lymphocyte. CLONAL EXPANSION: The activated B lymphocyte then divides, by mitosis, into plasma cells and memory cells |
| What are plasma cells? | Clones of the B lymphocyte. They secrete a lot of the antibody specific to the antigen into the blood |
| Antibodies are secreted by plasma cells. What do these antibodies go on to do? | These antibodies will bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes. This is the signal for the immune system to attack and destroy the pathogen |
| What is cell signalling? | How cells communicate |
| Complete the sentence: A cell may release (or _________) a substance that binds to the ___________ on another cell - this causes a ___________ of some kind in the other cell | A cell may release (or PRESENT) a substance that binds to the RECEPTORS on another cell - this causes a RESPONSE of some kind in the other cell |
| How is cell signalling used in the immune response? | Cell signalling helps to activate all the different types of white blood cells that are needed. For example, T helper cells release cytokines (interleukins) to activate B lymphocytes |
| Stains are often added to blood smear samples. Why? | Stains are added to blood smear samples to make the different cells easy to see |
| What are you likely to see when looking at a blood smear? | Red blood cells White blood cells Platelets |
| TRUE OR FALSE All types of white blood cell have granules in their cytoplasm | FALSE Only some types of white blood cell have granules in their cytoplasm, others do not |
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