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bio 3/4
responding to antigens
| Question | Answer |
|---|---|
| What is an antigen? | Unique molecule of parts of molecules that can trigger immune responses (immunogens). Can be self or non-self, eg. Virus, bacteria, toxins or parts of foreign organisms. |
| What is the structure of an antigen? | Protein based, one or more polypeptide chains. It is the structural differences that distinguish antigens from one another. |
| What are allergens and self-tolerance? | Allergens are antigens that trigger an allergic immune response. Self-tolerance is the inability to respond to self-antigens. |
| What is a cellular and non-cellular pathogen? | Cellular pathogens include bacteria, fungi, protozoans, worms (parasitic), and arthropods. Non-cellular pathogens are viruses, viroids, and prions. |
| What are physical barriers? | Plants include cutin and waxes on outer cell wall, and bark. Animal include intact skin and epithelial cells living in skin. |
| What are chemical barriers? | Plants include tannins in tea and grapes being toxic to insects. Animals include vaginal linings, and stomach acid. |
| What are microbiological barriers? | Non-pathogenic bacteria (normal flora) include skin, nose, throat, gastrointestinal and urogenital track. Prevents the growth of other bacteria, competes with resources, produces chemicals to reduce pH. |
| What are the characteristics of the innate system? | Non-specific, rapid, present in all animals, fixed (cannot adapt) and no immunological memory. |
| What are macrophages? | A type of phagocyte that moves into tissues to ingest foreign matter, dead neutrophils and tissue (clean up). |
| What is a neutrophil? | A type of phagocyte that ingests foreign material, then dies and forms pus. |
| What is a mast cell? | A large cell (not white blood cell) found in connective tissue. It contains histamine-filled granules that are released when involved in an allergen is encountered or in an inflammatory response. |
| What is a dendritic cell? | A type of phagocyte that is an antigen-presenting cell, once an unknown material is encountered, it travels to the lymph nodes to activate the adaptive immune response. |
| What is a complement protein? | A normally inactivated group of proteins that activate when exposed to bacterial/parasitic antigens, causing; activation of phagocytes and natural killer cells, attach to and identify non-self cells, attach to and lyse non-self cells. |
| What are the steps to combat an inflammatory response? | Bacteria enters an open wound. Cytokines/histamines/chemokines released attracting immune cells, blood vessel dilation. Neutrophils/macrophages phagocytose pathogen. Pathogen die, macrophage engulf. Wound healed, inflammatory response stops. |
| What are the characteristics of the adaptive immune response? | It is specific, and develops immunological memory to mount larger and more rapid response when exposed again. |
| What is humoral immunity? | B lymphocytes produce specific antibodies, they originate and differentiate in the bone marrow. B lymphocytes bind to antigens and begin dividing into plasma and memory cells. |
| What is the difference between B lymphocyte plasma and memory cells? | Plasma cells specialise in antibody production whereas memory cells remain in the lymphoid tissue and are responsible for immunity following infection or vaccination. |
| What is the antibody structure? | Y shaped protein. 4 polypeptide chains (2 heavy, 2 light) (quaternary), contains a variable region where the amino acid sequences that form the ‘top of the arms’ determine the specific antigen to bind to. |
| What is antibody function? | Neutralisation which prevents actions and invasion of bacterial toxins. Agglutination where antibodies bind to antigens on the surface forming antigen-antibody complex and activates phagocytes and complement cascade. |
| What is cell-mediated immunity? | Involves T helper cells, cytotoxic T cells, and suppressor T cells. |
| What are T helper cells? | Helps other cells of immune system, producing and secreting lymphocytes and interleukins. Cause B and T lymphocytes to divide and produce clones (some become T memory cells). Macrophages are also stimulated. |
| What are cytotoxic T cells? | Release powerful cytotoxins (perforin) which causes holes to form in cell membranes of antigens and enzymes that induce apoptosis. Primary cells responsible for fighting viral infection (kill off cells invaded by virus). |
| What are suppressor T cells? | Regulate action of lymphocytes and are able to suppress action of phagocytes – prevent overreaction. |
| How to T lymphocytes recognise antigens? | T lymphocytes distinguish between self and non-self-antigens by Major Histocompatibility Complexes (MHC). Normal body cells present MHC 1 to cytotoxic T lymphocytes. Specialised antigen presenting cells present antigen on MHC 2 to helper T lymphocytes. |
| Explain the primary response: | First encounter of T or B lymphocytes with specific antigen, memory B and T lymphocytes form IgM antibodies involved. |
| Explain the secondary response: | Lymphocyte and antibody production more rapid due to memory B and T lymphocyte, igG antibodies involved. |
| What are the functions of the lymphatic system? | It helps the immune system in defence by transporting white blood cells, transports excess tissue fluid that has leaked out of cells back to the bloodstream, absorption of fats from small intestine, and the site of lymphocyte maturation. |
| What are the primary lymphoid organs? | Bone marrow involves b and t lymphocyte production, and the thymus is the location of b and t lymphocyte maturation. |
| What are the secondary lymphoid organs? | The lymph nodes, spleen, tonsils, appendix, Peyer’s patches and adenoids. These are involved in lymphocyte activated and the beginning of the adaptive immune response. |
| What is the role of the lymph nodes? | The lymph nodes filter and trap foreign particles, cellular waste, toxins, and pathogens. They have dendritic cells and macrophages are stationed here. They also present foreign antigens to t lymphocytes – beginning the adaptive immune response. |
Created by:
lucyokane
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