01 The Immune System

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01 The Immune System

  1. 1. IMMUNITYThe Immune System ALBIO9700/2006JK
  2. 2. • Physical, chemical and cellular defences: – Epithelia that cover the airways – Hydrochloric acid in the stomach – Blood clotting – White blood cells ALBIO9700/2006JK
  3. 3. • Immunity – the protection against disease provided by the body’s defence or immune system• Antigen – any large molecule (e.g. protein) recognised by the body as foreign• Antibody – a protein made by the immune system in response to the presence of an antigen and targeted specifically at it• Immune response – lymphocytes respond to the presence of a pathogen in the body by producing antibodies ALBIO9700/2006JK
  4. 4. • Cells of the immune system are produced in the bone marrow• 2 groups of these cells involved in defence: – Phagocytes (neutrophils and macrophages) – Lymphocytes ALBIO9700/2006JK
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  6. 6. Phagocytes• Scavengers produced in bone marrow, removing any dead cells as well as invasive microorganisms• Neutrophils: – 60% of the white blood cells – Tissue ‘patrol’ – Released in large numbers from stores but are short-lived ALBIO9700/2006JK
  7. 7. • Macrophages: – Larger than neutrophils – Found in organs (lungs, liver, spleen, kidney and lymph nodes) – Leave bone marrow and travel in blood as monocytes – Long-lived – Initiates immune responses (cut pathogens up to display antigens) ALBIO9700/2006JK
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  9. 9. Phagocytosis ALBIO9700/2006JK
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  11. 11. Lymphocytes• Smaller than phagocytes with large nucleus• 2 types that are produced before birth in the bone marrow: – B lymphocytes (B cells) • Remain in bone marrow until mature • Spread throughout body (lymph nodes and spleen) – T lymphocytes (T cells) • Leaves bone marrow and mature in thymus • Coordinates the immune response, stimulating B cells to divide and then secrete antibodies into the blood • Seek out and kill any of the body’s own cells that are infected with pathogen ALBIO9700/2006JK
  12. 12. B lymphocytes• Each B cell makes just one type of antibody molecule• Cell divides to give small number of cells that make the same antibody (clone)• Antibody remains in plasma membrane and part of each antibody forms a protein receptor ALBIO9700/2006JK
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  15. 15. • Memory cells: – Basis of immunological memory (remain circulating for a long time, often lasting a lifetime) – Rapidly divide and develop into plasma cells and more memory cells upon reintroduction of antigen – Infection can be destroyed and removed before any symptoms develop – Leads to a faster secondary response ALBIO9700/2006JK
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  17. 17. Antibodies• Globular glycoproteins• Plasma protein (immunoglobulins)• Consists of: – 4 polypeptide chain (2 heavy and 2 light) – Disulphide bridges – 2 identical antigen binding sites – Variable region (specific shape that binds to just one antigen) – ‘hinge’ region (flexibility for antibody to bind around antigen) ALBIO9700/2006JK
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  20. 20. T lymphocytes• Have specific cell surface receptors (T cell receptors)• Activated when encounter antigen in contact with another host cell (e.g. macrophage or invaded body cell)• 2 types: – T helper cells • Secrete cytokines – stimulate B cells to divide and stimulate macrophage to carry out phagocytosis more vigorously – killer T cells (T cytotoxic cells) • Search invaded body cells, attach themselves and secrete toxic substances (hydrogen peroxide) ALBIO9700/2006JK
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