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Specific immune system

Specific immune system. B-lymphocytes. Immune system diseases. Non specific immunity. Disease survival mechanisms. Physical & chemical barriers. Infectious Disease. Inflammatory. Transmission. Epidemiology. Non-specific Cellular response. Specific immunity. Public Health. Vaccination.

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Specific immune system

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  1. Specific immune system B-lymphocytes

  2. Immune system diseases Non specific immunity Disease survival mechanisms Physical & chemical barriers Infectious Disease Inflammatory Transmission Epidemiology Non-specific Cellular response Specific immunity Public Health Vaccination Immunological surveillance T cells B cells Clonal Selection theory Big picture

  3. Learning outcomes • Explain the role of lymphocytes, B cells in the immune system • Identify The need for immunological memory • Apply the Importance of primary and secondary responses

  4. Third line of defence • Specific (only acts on particular pathogen) • First immunological surveillance occurs to find/ discover pathogen • Then clonal selection needs to occur to find the corresponding lymphocyte to combat the pathogen

  5. B lymphocytes (b cells) • AN ANTIGEN IS A COMPLEX MOLECULE – RECOGNISABLE AS SELF OR FOREIGN/ NON-SELF • ANTIGEN TRIGGERS PRODUCTION OF ANTIBODIES • ANTIBODY IS A Y-SHAPED MOLECULE WITH A SPECIFIC RECEPTOR (BINDING SITE) • Lymphocytes respond specifically to antigens on foreign cells, cells infected by pathogens and toxins released by pathogens.

  6. Antigen - any agent capable of eliciting an immune response Isolated molecules Molecules on surface of cell or virus * A specific antibody molecule will be able to recognize a specific (epitope ) antigen Antibody binds to antigen Specific Immunity Antibody-Antigen Interaction

  7. B Cell activation B CELLS PLAY THREE IMPORTANT ROLES IN THE IMMUNE RESPONSE: • THEY PRODUCE ANTIBODIES IN RESPONSE TO SPECIFIC ANTIGENS • THEY PERFORM THE ROLE OF ANTIGEN-PRESENTING CELLS • THEY DEVELOP INTO MEMORY B CELLS.

  8. B CELL ANTIBODIES EACH B CELL CAN A PRODUCE A SPECIFIC ANTIBODY THAT CAN RECOGNISE A SPECIFIC ANTIGEN FROM A PATHOGEN OR TOXIN. THE ANTIBODY WILL BIND TO THE ANTIGEN, FORMING AN ANTIGEN–ANTIBODY COMPLEX. THE ANTIGEN–ANTIBODY COMPLEX HAS TWO MODES OF ACTION: • IT MAY INACTIVATE THE PATHOGEN/TOXIN (NEUTRALISATION), RENDERING IT SUSCEPTIBLE TO PHAGOCYTOSIS. • IT MAY STIMULATE A RESPONSE, RESULTING IN CELL LYSIS.

  9. Agglutination • Antibodies can cause microbes to stick together • This makes it easier for phagocytes to engulf them

  10. Inactivate • Antibodies can bind to pathogen • Causing them to become inactive / rendering them harmless

  11. Neutralisation • Some pathogens make us ill by producing toxins • Some antibodies work by neutralising these toxins

  12. Stimulate cell lysis • The binding of an antibody to the surface of a pathogen can set of a chain reaction with blood proteins, which... • ... causes the pathogen to swell up an burst.

  13. Need a little help from my friends .... • B cells can identify specific antigens and present them to T cells. • T cells can then destroy the pathogen.

  14. Signal 2 - T cell help B Th Th Y Y Y * T Helper Cells 1. T cell antigen receptor 2. Co-receptor (CD4) Signal 1antigen & antigenreceptor 3.CD40 Ligand

  15. SIGNAL More About T-Lymphocytes Help the humoral response by involvement in the maturation of B cells and by triggering the production of antibodies by B-cells Helper T-cells: Antigen B-cell Helper T-cell

  16. Clonal selection theory • The body has a large number of lymphocytes each with a single type of membrane receptor specific for one antigen. • When a receptor is activated by the binding of an antigen, the lymphocyte repeatedly divides resulting in a clonal population of lymphocytes. Cell division

  17. Summary slide Specific defences Immune surveillance • A range of white blood cells constantly circulate monitoring the tissues. • If tissues become damaged or invaded, cells release cytokines which increase blood flow resulting in specific white blood cells accumulating at the site of infection or tissue damage. • Recognition of self and non self through specific surface proteins (antigens) • Lymphocytes respond specifically to antigens on foreign cells, cells infected by pathogens and toxins released by pathogens.

  18. Summary slide specific defences B lymphocytes • Each B lymphocyte clone produces a specific antibody molecule that will recognise a specific antigen surface molecule on a pathogen or a toxin. • Antigen-antibody complexes may inactivate a pathogen or toxin or render it more susceptible to phagocytosis. • In other cases the antigen-antibody complex stimulates a response which results in cell lysis. • B lymphocytes activated by antigen presenting cells and T lymphocytes produce a clone of B lymphocytes that secrete antibodies into the lymph and blood where they make their way to the infected area.

  19. Summary slide Specific defences Immunological memory cells • Some T and B lymphocytes produced in response to antigens by clonal selection survive long term as memory cells. • A secondary exposure to the same antigen rapidly gives rise to a new clone of lymphocytes producing a rapid and greater immunological response.

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