Immune Response - PowerPoint PPT Presentation

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Immune Response

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  1. Immune Response (Specific) Each response is directed towards a specific micro-organism Humoral Cell Mediated (antibody mediated) (lymphoctyes) B Cells In Lymphoid T Cells Tissue Mature in Bone marrow Mature in Thymus Both are Produced in Bone Marrow

  2. Antigens “Any substance capable of causing a specific immune response” • Can be protein, carbohydrate, lipid or nucleic acid • Can be whole micro-organism, or part of bacterium (eg Flagella), or toxins produced by bacterium. Self-Antigens “Large molecules produced in person’s own body & don’t cause immune response” Non-Self Antigen “Foreign compounds that DO trigger an immune response”

  3. Antibodies “ A specialised protein that is produced in response to a NON-SELF antigen • Antigen molecules have specific active sites & it is here that antibody can combine with the antigen = Antigen-antibody complex • Lock & Key Model

  4. T Lymphocytes (T cells) • “Educated” in the thymus • Migrate into the bloodstream, lymph nodes & lymphoid tissue • Highly mobile and continually circulate throughout the body • Involved in cell-mediated immunity • Provides resistance once foreign micro-organism enters cell

  5. B Lymphocytes (B cells) • “Educated” in red bone marrow • Released into bloodstream, migrate to lymph nodes & lymphoid tissue • Less mobile than T cells • Shorter life span • Replaced continuously • Involved in antibody-mediated immunity (Humoral) • Provides resistance BEFORE micro-organism enters cell.

  6. Similarities of B & T Cells • Both are antigen specific • Will only react to those antigens they have been trained to recognise • Both develop a memory • Once they have been exposed to the specific antigen they are able to respond more quickly on subsequent exposures

  7. Antibody-Mediated Immunity (Humoral) • B cells involved • B cells can become activated in two ways: • Macrophages can ingest the pathogen and then present the antigen to a B cell • Antigen makes direct contact with a B cell

  8. Activation of B cell occurs if the antigen matches the receptor located on the B cell • Once activated: • B cell enlarges • Undergoes repeated mitotic division • Most of the millions of resulting daughter cells become plasma cells • Plasma cells secrete antibody into the lymph • Some B daughter cells – memory cells (allow response to occur quicker on subsequent exposure)

  9. Secreted antibody circulates throughout body until it comes into contact with matching antigen • Antibody reacts with antigen to form antigen-antibody complex All antibodies combine with the antigen for which they are specific.

  10. Responses • Combine with foreign enzymes/toxins to inactivate them & inhibit reactions • Bind to viruses surface to prevent virus entering cells • Coat bacteria therefore bacteria easier to consume by phagocytes • Cause bacteria, viruses or foreign blood cells to clump together – agglutination • Dissolve organisms • React with soluble substances to make them insoluble therefore easily consumed

  11. Summary of B Cells… One type of B cell is activated B cells Clones are produced Plasma Cells secrete antibodies Circulate until find antigen Memory cells Spread to all tissues

  12. Cell-Mediated Immunity • T cells can only react to an antigen if the antigen has entered a cell • Very good at counteracting viral diseases • Cell is able to alert the immune system by displaying non-self proteinfragments on outer surface

  13. Thousands of different T cells made to interact with specific antigen • Once activated: • T cell divides rapidly forming clone cells • T killer cells (cytotoxic T cells) leave lymph nodes and migrate to infection site • Attack infected cells directly by lysing (breakdown of cell wall) them • Attract macrophages to engulf cells • Releasing a substance that speeds up macrophage activity • Activate other lymphocytes

  14. T helper cells secrete substances that amplify and control immune system • E.g. responsible for activating B & T cells • T memory cells which enhance the secondary response to any subsequent infection

  15. Summary of T cells… T cells in lymphoid tissue 1 type of T cell sensitised Clones produced Killer T cells go to site of infection Memory Cells Attach to antigen, enhance & increase macrophages

  16. Exposure to antigens Antigens 2nd Exposure More rapid due to memory cells Initial Exposure

  17. Lymphokines • Soluble substances released by sensitised lymphocytes when the come into contact with antigen • Inhibit multiplication of pathogens • Attract phagocytes • Secrete interferon (blocks viral infection) • Activate macrophages

  18. Interleukins • Interleukin-1 • Released by macrophages • Activates helper T cells • Helper T cells secrete Interleukin-2 • Interleukin-2 • Stimulates killer T cells to divide rapidly