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Non specific
immunity
Inflammatory
Non-specific Cellular
response
Physical & chemical barriers
Specific immunity
Immunological surveillance
Clonal Selection
theory
T cellsB cells
Infectious Disease
Transmission
Epidemiology
Vaccination Public Health
Immune system
diseasesDisease survival
mechanisms
Big picture
Learning outcomes
• Identify the variety of t lymphocytes.
• Examine the action/function for each t cell population
Third line of defence
• Specific (only acts on particular pathogen)
• Involves lymphocytes
Line of defenc
e
Specific (s) or non-
specific (ns)
Mechanism employed Function
3rd S Antibodies production from B cells from bone marrow
Make antibodies (humoral response)and are found in the lymphoid organs (except the thymus)3rd S Response by T cells from
thymus glandCellular immunity but also with the regulation of the humoral response
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.
Helper t cells (tH cells)
• Helper t cells (tH cells) ; secrete cytokines
that activate phagocytes, t cells and b cells.
Instead they produce cytokines – a chemical signal that activate B lymphocytes and phagocytes, which can then act to destroy the infected cell.
Helper T cells are not able to destroy infected cells.
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.
Killer T-cells: Can attach themselves to cells with foreign antigens on their surface and destroy them
1. Virus attaches to and enters host cell
2. Viral DNA causes host cell to express viral anitgens on its surface
3. Killer T-cell attaches to viral
antigen on infected cell
4. Killer T-cell induces death of
infected cell
Killer T-cells and cancer:
1. As cell becomes cancerous mutations take place
2. Mutations cause cancerous cell to express abnormal antigens
3. Killer T-cell binds to abnormal antigens
4. Killer T-cell induces death of
cancerous cell
(Usually)
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.
* T Helper Cells
YYY
B
Signal 1antigen & antigen
receptor
Th
1. T cell antigen receptor
2. Co-receptor (CD4)
3.CD40 Ligand
Th
Signal 2 - T cell help
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.
Summary slide
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.
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.
•
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
Line of defenc
e
Specific (s) or non-
specific (ns)
Mechanism employed Function
3rd S Antibodies production from B cells from bone marrow
Make antibodies (humoral response)and are found in the lymphoid organs (except the thymus)3rd S Response by T cells from
thymus glandCellular immunity but also with the regulation of the humoral response
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.
•