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Specific Immune System

Specific Immune System. T - 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.

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Specific Immune System

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  1. Specific Immune System T - 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 • Identify the variety of t lymphocytes. • Examine the action/function for each t cell population

  4. Third line of defence • Specific (only acts on particular pathogen) • Involves lymphocytes

  5. lymphocytes • LYMPHOCYTES ARE A TYPE OF WHITE BLOOD CELL. THERE ARE A NUMBER OF DIFFERENT TYPES OF LYMPHOCYTE; • TWO OF THE MOST IMPORTANT ARE B LYMPHOCYTES AND T LYMPHOCYTES. • T LYMPHOCYTES ARE ALSO CALLED T CELLS. THEY ARE FORMED IN THE THYMUS GLAND – HENCE THEIR NAME. • T LYMPHOCYTES PLAY AN IMPORTANT ROLE IN THE IMMUNE SYSTEM AND THEY ACCOUNT FOR MORE THAN 4/5 FOUR-FIFTHS OF CIRCULATING LYMPHOCYTES. • THERE ARE TWO MAIN GROUPS OF T LYMPHOCYTES: • CYTOTOXIC T CELLS • HELPER T CELLS.

  6. Helper t cells (tH cells) • Helper t cells (tH cells) ; secrete cytokines that activate phagocytes, t cells and b cells. Helper T cells are not able to destroy infected cells. Instead they produce cytokines – a chemical signal that activate B lymphocytes and phagocytes, which can then act to destroy the infected cell.

  7. Cytotoxic t cells (tc cells) • CYTOTOXIC T CELLS (TC CELLS) ; DESTROY INFECTED CELLS BY SEVERAL METHODS INCLUDING THE INDUCTION OF APOPTOSIS • THE CYTOTOXIC T CELLS ARE ALSO CALLED KILLER T CELLS. THEY RECOGNISE ANTIGENS ON INFECTED CELLS, BIND TO THE ANTIGEN AND CAN DESTROY THE CELLS BY APOPTOSIS. • APOPTOSIS IS A FORM OF PROGRAMMED CELL DEATH – THE CELL IS INSTRUCTED TO DESTROY ITSELF.

  8. Killer T-cells: Can attach themselves to cells with foreign antigens on their surface and destroy them 2. Viral DNA causes host cell to express viral anitgens on its surface 1. Virus attaches to and enters host cell 3. Killer T-cell attaches to viral antigen on infected cell 4. Killer T-cell induces death of infected cell

  9. Killer T-cells and cancer: 2. Mutations cause cancerous cell to express abnormal antigens 1. As cell becomes cancerous mutations take place 3. Killer T-cell binds to abnormal antigens 4. Killer T-cell induces death of cancerous cell (Usually)

  10. Memory cells • Once cytotoxic T cells have completed their job, the majority of cells undergo apoptosis. • HOWEVER, A FEW CELLS BECOME ‘MEMORY CELLS’, WHICH WILL REMAIN ON HAND TO RESPOND SHOULD THE ANTIGEN REAPPEAR AT SOME POINT IN THE FUTURE.

  11. 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

  12. Summary slide specific defences T lymphocytes • One group of T lymphocytes destroy infected cells by inducing apoptosis. • Another group of T lymphocytes secrete cytokines that activate B lymphocytes and phagocytes. • When pathogens infect tissue, some phagocytes capture the pathogen and display fragments of its antigens on their surface. • These antigen presenting cells activate the production of a clone of T lymphocytes that move to the site of infection under the direction of cytokines.

  13. Summary slide SPECIFIC DEFENCES T LYMPHOCYTES • T LYMPHOCYTES HAVE SPECIFIC SURFACE PROTEINS THAT ALLOW THEM TO DISTINGUISH BETWEEN THE SURFACE MOLECULES OF THE BODY’S OWN CELLS AND CELLS WITH FOREIGN MOLECULES ON THEIR SURFACE.

  14. 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.

  15. 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

  16. Cytotoxic t cells (tc cells) • CYTOTOXIC T CELLS (TC CELLS) ; DESTROY INFECTED CELLS BY SEVERAL METHODS INCLUDING THE INDUCTION OF APOPTOSIS • THE CYTOTOXIC T CELLS ARE ALSO CALLED KILLER T CELLS. THEY RECOGNISE ANTIGENS ON INFECTED CELLS, BIND TO THE ANTIGEN AND CAN DESTROY THE CELLS BY APOPTOSIS. • APOPTOSIS IS A FORM OF PROGRAMMED CELL DEATH – THE CELL IS INSTRUCTED TO DESTROY ITSELF. • ONCE CYTOTOXIC T CELLS HAVE COMPLETED THEIR JOB, THE MAJORITY OF CELLS UNDERGO APOPTOSIS. • HOWEVER, A FEW CELLS BECOME ‘MEMORY CELLS’, WHICH WILL REMAIN ON HAND TO RESPOND SHOULD THE ANTIGEN REAPPEAR AT SOME POINT IN THE FUTURE.

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