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Immunology
CAPE Biology Unit 2
| Question | Answer |
|---|---|
| What is the difference between a parasite and a pathogen? | A parasite can live in or on host without causing harm. A pathogen causes harm to the host and cause disease. |
| Why are viruses and prions NOT considered to be 'organisms'? | They have no cells and no metabolism. |
| To which group of pathogens do DENV, HIV and Epstein-Barr belong? | Viruses |
| To which group of pathogens do Vibrio cholera (cholera), Mycobacterium tuberculosis (TB) and Clostridium tetani (tetanus) belong? | Bacteria |
| To which group of pathogens do Plasmodium falciparum(malaria) and Trypanosoma cruzi (Chagas disease) belong? | Protoctista |
| To which group of pathogens do Candida albicans (thrush) and Pneumocystis jiroveci (pneumonia) belong? | Fungi |
| To which group of pathogens do Schistosoma mansoni (schistosomiasis or bilharzia) and Necator americanus (hookworm) belong? | Worms |
| To which group of pathogens does Creutzfeldt-Jakob Disease (CJD) belong? | Prions (infectious proteins) |
| What are six ways in which pathogens can enter the body? | 1) Mosquito injection 2) Blood to blood 3) Sexual contact 4) Air droplets 5) Food 6) Water |
| What are the three main categories of defence against infectious diseases? | 1) Mechanical 2) Chemical 3) Cellular |
| Tissues provide physical barriers that pathogens cannot pass through unaided. This type of defence is | Mechanical |
| Substances secreted by the body provide inhospitable environments for pathogens, trap them, cause them to burst, stop them reproducing and/or growing, stop them entering cells and kill them. This type of defence is | Chemical |
| Cells secrete hormone-like chemicals to alert the body to the presence of pathogens; ingest and digest pathogens; secrete chemicals to protect the body against the spreading of pathogens.This type of defence is | Cellular |
| When pathogens enter the body, where can they go? | 1) Spaces between cells 2) Into the cells |
| What is a possible effect of worms living in the gut? | Reduced (less) quantity of digested food. Less nutrients available for the body. |
| What are 4 characteristics of the NON-SPECIFIC defences of the immune system? | 1) Present from birth (innate) 2) Does not distinguish between different pathogens 3) Gives the same response each time a particular pathogen enters the body. 4) Rapid response but not always highly effective. |
| What are the two mechanical defences in the body? | 1) Skin 2) Mucous membranes eg. in the trachea, bronchioles, vagina, gut. |
| Name the chemical responsible for the following mode of action. 'Provide inhospitable environment with low pH.' | Lactic acid, fatty acids, hydrochloric acid... |
| Name the chemical responsible for the following mode of action. 'Hormone-like action to stimulate cellular defences.' | Histamine |
| Name the chemical responsible for the following mode of action. 'Hormone-like action to protect cells against viruses.' | Interferon |
| Name the chemical responsible for the following mode of action. 'Hormone-like action to regulate the immune system.' | Interleukins |
| Name the chemical responsible for the following mode of action. 'Proteins that help mark and remove pathogens from the body.' | Complement |
| Name the chemical responsible for the following mode of action. 'Aggregate, immobilise and kill pathogens; neutralise toxins, prevent entry of pathogens into cells.' | Antibodies |
| State 4 main types of cells involved in cellular defence. | 1) Phagocytes (neutrophils and macrophages) 2) Mast cells 3) B-lymphocytes(plasma cells) 4) T-lymphocytes |
| What is the role of phagocytes in cellular defence? | Ingest and digest pathogens; present antigens |
| What is the role of mast cells in cellular defence? | Secretion of histamine |
| What is the role of B-lymphocytes? | Secretion of antibodies |
| What is the role of T-lymphocytes? | They coordinate the response of pathogens, kill infected cells. |
| What are 4 characteristics of the SPECIFIC defences of the immune system? | 1) Not present from birth 2) Highly specific to particular pathogens 3) It is adaptive, responding to changes in the environment/pathogen. 4) Slower than non-specific responses but more effective. |
| What is the effect of interleukin 1 released by macrophages? | Interleukin 1 stimulates the brain, causing fever and sleepiness. Fever is one of our non-specific defences. |
| A cut in the skin occurs. What happens next? | Upon detection of pathogens 1) Mast cells release histamine (a hormone) by exocytosis. 2) Histamine diffuses to adjacent target cells and stimulate inflammation. 3) Complement proteins combine with the pathogen and attach to mast cell receptors. |
| What are five changes which occur when a tissue becomes inflamed? | 1) Capillaries become leaky 2) White blood cells enter tissues 3) Plasma proteins (complement and antibodies) enter tissues 4) Area becomes hot, red and swollen 5) Tissue phagocytes (macrophages) are activated to engulf bacteria |
| List the five steps involved in phagocytosis. | 1) Chemotaxis 2) Adherence 3) Fusion 4) Killing 5) Digestion |
| Name the process by which neutrophils, macrophages and other phagocytes engulf pathogens and other foreign particles. | Endocytosis |
| What does MHC stand for? | Major histocompatibility complex. |
| What are macrophages? | Tissue phagocytes |
| What do MHC class II proteins do? | They 'present' antigens which have been partially processed by macrophages to cells of the specific immune system. |
| State two types of molecules/cells which can can function in antigen presentation. | Both MCH Class II proteins and B-lymphocytes can present antigens to the cells of the specific immune system. |
| Why are they called 'complement' proteins? | They help antibodies get rid of bacteria. They can work without antibodies but work best with them. |
| What are complement proteins? | A group of 20-25 proteins which are stimulated by pathogens (and antibodies). They stimulate a range of defences including phagocytosis. |
| What are two ways complement (C3 specifically) can become activated? | 1) Antibodies attached to bacteria 2) Bacterial/fungal cell walls These activate enzymes in a cascade. These trigger complement activity. |
| What are three effects of active complement (C3 protein) in inflammation? | 1) Stimulate mast cells to release histamine 2) Attract neutrophils from blood 3) Makes capillaries more permeable |
| How does complement (C3) affect phagocytosis? | 1)Forms membrane attack complex with other complement proteins leading to lysis of bacteria. 2)Attaches to receptors on phagocytes which engulf and destroy bacteria. |
| What happens in the non-specific defence against viruses? | 1) Interferon is released (hormone-like chemical) 2) Interferon activates the production of antibodies and the T-lymphocytes that destroy infected cells. |
| What are the 2 main groups of lymphocytes in the immune response? | B-lymphocytes (B-cells) and T-lymphocytes (T-cells) |
| What is the origin of T and B lymphocytes? | Bone marrow |
| What makes B-cells specific? | Each type of B-cell has a different shaped B-cell receptor (BCR) that identifies its specificity. |
| What makes T-cells specific? | Each type of T-cell has a T-cell receptor (TCR) that identifies its specificity. |
| What is one main difference between T and B cells re antibodies? | B- cells release antibodies. T-cells do not. |
| Where are B-cells matured? | They mature in the bone marrow. |
| Where are T-cells matured? | They mature in the thymus gland. |
| During the maturation process of T and B-cells, which cells are eliminated? | Cells with receptors that have a high affinity for 'self' antigens. |
| Why are all T-cells which recognize 'self' antigens killed in the thymus gland? | To ensure that the immune system does not destroy the body's own cells. |
| Where do T and B cells go after maturation? | Lymphoid tissue throughout the body |
| What does CD stand for with respect to receptors? | Cluster of differentiation |
| What happens to immature lymphocytes if they do not develop CD receptors? | They are killed |
| Which lymphocyte has CD20 receptors? | B-lymphocytes |
| Which lymphocytes have CD4 receptors? | Helper T-lymphocytes |
| Which lymphocytes have CD8 receptors? | Cytotoxic T-lymphocytes |
| Which lymphocytes have CD4 and CD8 receptors? | Regulatory(suppressor) T-lymphocytes |
| What is the function of B-lymphocytes? | 1) Present antigens to helper T-cells 2) Differentiate into plasma cells that secrete antibodies. |
| What is the function of helper T-lymphocytes? | 1) Respond to antigens presented by cells with MHC class II proteins 2) Secrete cytokines to stimulate B-cells, cytotoxic T-cells and non-specific defences. |
| What is the mode of action of cytotoxic T-lymphocytes? | 1) Respond to antigens presented by cells with MHC class I proteins 2) Attack cells infected with intracellular parasites. 3) Attack cancer cells and transplanted tissues. |
| What is the role of regulatory(suppressor) T-lymphocytes? | 1) Regulate the specific defence system 2) Suppress auto-immunity |
| Where in the body can lymphocytes be found? | Blood, lymph, lymph nodes, spleen and liver |
| What is the role of CD4 and CD8 receptors? | They stabilize the interaction between the cell receptors (BCRs and TCRs) and the MHC proteins on antigen-presenting cells. |
| What are the two types of MHC proteins? | MHC class I and MHC class II |
| What does the term "humoural" refer to in immunology? | Body fluids |
| What is the main characteristic of the specific defence system? | Immune responses |
| What is clonal selection? | The activation of clones of lymphocytes which have receptors (BCRs and TCRs) complementary to the antigens present. |
| What is clonal expansion? | The production of many more activated lymphocytes by mitosis. |
| This type of response involves the production of antibodies. | Humoral immune response. |
| Why are antibodies only effective against extracellular pathogens? | Antibodies are proteins and as such they cannot cross cell membranes. |
| This type of response involves cytotoxic T-cells. | Cell-mediated immune response. |
| Which type of immune response occurs against intracellular parasites? | Cell-mediated immune response. |
| What is the name of the phagocytic cells which exist in the skin ? These are the first to be infected by dengue viruses. | Langerhans cells |
| What happens when a B-cell encounters large polysaccharide molecules on the surface of bacteria? | Many BCR receptors interact with the antigen. The B-cell becomes activated to divide and differentiate into plasma cells. |
| What happens when a B-cell encounters small, single unit antigens? | Single BCR interacts with the antigen and takes it into the B-cell by endocytosis. They are processed into MHC class II proteins and presented on cell surface for T-cells to detect. |
| What role do T-cells play in humoral immune response? | Helper T-cells with TCRs complementary to the antigen bind to the B-cell (which is presenting an antigen). They secrete cytokines that activate the B-cell to divide and differentiate. |
| What is the function of CD4 proteins on T-helper cells? | They stabilize the interaction between MHC protein, antigen and TCR. |
| What are two possible pathways of activated B-cells? | 1) They can form (differentiate into) plasma cells which secrete antibodies. 2) They differentiate into memory cells |
| What is the main feature of cell-mediated immune response? | Cytotoxic T cells are activated to attack and kill infected host cells. |
| What causes asthma? | Immune response of certain lymphocytes to harmless antigenic material such as pollen grains and dust mites. |
| What is the role of T-helper cells in cell-mediated immune response? | Helper T cells detect antigen presenting cells. Those with complementary TCRs to the antigen bind to MHC-antigen complex. They secrete cytokines which activate the macrophages to kill the pathogens within them. |
| What is the role of cytotoxic T-cells in cell-mediated immune response? | They patrol for infected host cells which express foreign antigens in their MHC class I proteins. If their TCR is complementary to the antigen, they secrete perforins that 'punch' holes and kill the cells. |
| What is the roles of CD8 proteins on cytotoxic T cells in cell mediated response? | They help to stabilize the interaction between MHC class I protein, antigen and TCR. |
| What happens to cytotoxic T cells after they have become activated by detecting infected cells? | 1) They divide by mitosis. 2) Some become memory cells, others patrol the blood in search of other infected cells. |
| What are memory cells? | They are representatives of (the clones of) B and T cells. Since there are more of them on a secondary infection, a much faster response is produced. They are the basis of long-term immunity. |
| What are immunoglobulins (Ig) ? | Antibodies (plasma proteins) |
| What level of protein organization is exhibited by antibodies? | Quaternary |
| What is the simplest class of antibody molecules? | Ig class G (IgG) |
| What type of bond joins the four polypeptide chains of an antibody molecule? | Disulphide bond |
| What is the role of the hinge region of an antibody? | Provides flexibility to the binding sites. |
| What region of an antibody molecule is identical in all antibodies of the same class? | The constant region. |
| What are the four classes of antibody molecules? | IgA , IgE, IgG and IgM |
| What is the role if IgA? | 1) Inhibits adherence of bacteria to host cells. 2) Prevents bacteria forming colonies on mucous membranes. |
| What is the role of IgE? | Constant region activates mast cells during infections and also to dust mites and pollen (allergic reaction). |
| What is the role of IgG? | 1) Activates complement proteins 2) Helps macrophages engulf pathogens 3) Neutralizes toxins 4) Causes agglutination of bacteria |
| What is the role of IgM? | 1) Activates complement proteins 2) Causes agglutination of bacteria |
| Which 2 classes of antibodies have only 2 antigen binding sites? | IgE and IgG |
| Which class of antibodies can have 2 or 4 antigen binding sites? | IgA |
| Which class of antibodies has 10 antigen binding sites? | IgM |
| What is formed when an antibody attaches to an antigen? | An antigen-antibody complex |
| What are seven roles of antibodies? | 1) Agglutination of bacteria 2) Immobilization of bacteria 3) Prevent entry of pathogens into cells 4) Neutralization of toxins 5) Breaking open bacteria 6) Coating pathogens to enhance phagocytosis 7) Activating complement protein(C3) |
| Describe the role of antibodies in agglutination of bacteria. | By binding to two or more bacteria, antibodies prevent them spreading and hold them together to make bigger targets for phagocytes. |
| Describe the role of antibodies in immobilization of bacteria. | Antibodies bind to the flagella of some types of bacteria preventing them from moving. |
| Describe the role of antibodies in preventing entry of pathogens into cells. | Antibodies that bind to the surface proteins of viruses and bacteria prevent them making contact with proteins on the surface of host cells. This prevents viruses, such as DENV, from entering cells and being replicated. |
| Describe the role of antibodies in neutralization of toxins. | Some bacteria release toxins, which often have very severe side effects. Examples are botulinum toxin, tetanus toxin, diphtheria toxin and choleragen from cholera bacteria. Antibodies that form complexes with toxins to make them harmless are antitoxins. |
| Describe the role of antibodies in breaking open bacteria. | Lysins are antibodies that combine with other proteins to break open bacterial cell walls. The cytoplasm of bacteria has a lower water potential than body fluids, so water enters by osmosis and the bacterial cells burst. |
| Describe the role of antibodies in coating pathogens to facilitate phagocytosis. | Antibodies that attach to bacteria help to 'mark' them for destruction by phagocytes. This is called opsonisation. |
| Describe the role of antibodies in activating complement protein. | Some antibodies activate one of the cascade systems that activates complement protein, C3. |
| Why does the primary immune response take a while to occur? | Upon presentation of antigen, it takes a while for the specific antibody molecules to appear in the plasma. This is because clonal selection and clonal expansion have to take place before there are plasma cells able to secrete the appropriate antibody. |
| Why is the secondary immune response much faster than the primary? | This is because there are many more cells of the appropriate B-cell clone(memory cells) to differentiate into plasma cells. This results in a much faster production of antibody molecules. |
| Why does HIV affect T-cell count? | HIV infects helper T-cells with the CD4 protein. It results in the T-cell bursting open (becoming destroyed). This decreases number of T-cells in the blood. |
| What characterizes active immunity? | An immune response, long term to life-long protection. |
| What is the difference between natural active immunity and artificial active immunity? | Natural active - occurs upon infection (unintentional exposure) Artificial active - occurs when you are given a vaccine that contains an antigen. |
| What is the difference between natural passive and artificial active immunity? | Natural passive - when baby received antibodies from mother through placenta and breastmilk. Artificial passive - antibodies are injected into an individual giving rise to instant immunity. |
| Breastmilk is rich in this type of antibody. | IgA |
| What is the main advantage of active immunity? | Immunity is long term. |
| What is the main advantage of passive immunity? | Immediate protection. |
| What are two disadvantages of active immunity? | Response takes time/protection not immediate. Symptoms may develop/may be fatal. |
| What are two disadvantages of passive immunity? | Immunity is short term/antibodies gradually destroyed. No memory cells produced. |
| What is herd immunity? | Resistance to the spread of an infectious disease within a population that is based on pre-existing immunity of a high proportion of individuals as a result of previous infection or vaccination. - Oxford dictionary |
| What is ring vaccination? | The vaccination of all susceptible individuals in a prescribed area around an outbreak of an infectious disease. This is achieved through surveillance. |
| What is a polyclonal response? | This is an immune response to a wide range of different antigens. As a result, many clones of B-cells and T-cells are selected and activated. |
| What is the benefit of producing antibodies from single clones of B-cells? | Each clone of B-cells produces one type of antibody with a highly specific antigen binding site. |
| What was the main problem with isolating B-cells in the lab? | B-cells do not survive if kept in tissue culture. |
| How did scientists get B-cells to survive in tissue culture? | They fused the B-cells with malignant tumour cells (myeloma cells) which survive and divide in culture. The fused cells are called hybridoma cells. |
| What are the stages in producing monoclonal antibodies (Mabs) in the lab? | 1) Injection of specific antigenic material into a small mammal 2) After weeks, B-cells are isolated from animal's spleen 3) These B-cells are fused with myeloma cells to form hybridoma cells 4)Desired antibodies produced are isolated and purified. |
| List 5 uses of Mabs. | 1) Blood type tests 2) Pregnancy tests 3) STD detection 4) Cancer treatment 5) Tissue typing Etc etc etc |
| What is the difference between a non-specific and a specific response? | In non-specific response, phagocytes can attack and destroy any type of non-self material. In a specific response, each lymphocyte is specialized in recognizing and responding to one particular antigen. |
| What are the two main types of phagocytes? | 1) Neutrophils - make up 60% blood, short-lived, constantly replaced. 2) Macrophages (monocytes) - long lived, function as antigen presenting cells. |
| What do antigen presenting cells (macrophages) do? | They break down foreign particles (pathogens) and place some of the molecules in their plasma membranes. These molecules are displayed to other cells of the immune system to identify and destroy the invaders. |
| Name two groups of substances which can enhance phagocytosis. | Complement - a group of proteins Cytokines - chemicals released by lymphocytes |
| Define pathogen | A pathogen may be defined as a microorganism that causes disease. |
| Define parasite | A parasite is an organism that lives in very close relationship with another organism, called its host, and does it harm. The parasite gains from the relationship. |
| What is the relationship between parasites and pathogens? | All pathogens are parasites but not all parasites are pathogens. |
| Define immune response. | The immune response is the way in which the immune system responds to the presence of non-self cells or molecules in the body. |
| Why are T-lymphocytes more effective than B-lymphocytes in dealing with viral infections? | T-killer lymphocytes can destroy virally infected cells directly. B-lymphocytes release antibodies which destroy the bacteria to which they bind. |
| A type of white blood cell that divides to produce plasma cells, which secrete antibodies. | B-lymphocyte |
| A phagocytic white blood cell with a multilobed nucleus and granular cytoplasm. | Neutrophil |
| A molecule that is recognized by lymphocytes as being foreign to the body. | Antigen |
| An organism that lives in close association with a host and does it harm. | Parasite |
| A microorganism that causes disease. | Pathogen |
| A glycoprotein secreted by some white blood cells, which binds to specific antigens. | Antibody |
| A phagocytic white blood cell that is relatively large, and which tends to be found in tissues such as the lungs rather than in the blood. | Macrophage. |
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Ms.Kumar
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