Transcript File
SPECIFIC IMMUNE
SYSTEM
B-LYMPHOCYTES
Immune system
diseases
Non specific
immunity
Disease survival
mechanisms
Physical &
chemical barriers
Infectious
Disease
Inflammatory
Non-specific
Cellular response
Specific
immunity
Transmission
Epidemiology
Vaccination
Public Health
Immunological
surveillance
T cells
B cells
Clonal Selection
theory
BIG PICTURE
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
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
Specific (s) or
defence 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
gland
Cellular immunity but also with the
regulation of the humoral response
B LYMPHOCYTES (B CELLS)
• LYMPHOCYTES RESPOND SPECIFICALLY TO ANTIGENS ON FOREIGN
CELLS, CELLS INFECTED BY PATHOGENS AND TOXINS RELEASED BY
PATHOGENS.
• 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)
SPECIFIC IMMUNITY
ANTIBODY-ANTIGEN INTERACTION
• 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
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.
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.
Agglutination
Antibodies can cause
microbes to stick
together
This makes it
easier for
phagocytes to
engulf them
Inactivate
Antibodies can bind to pathogen
Causing them to become
inactive / rendering them harmless
Neutralisation
Some pathogens make us ill by producing toxins
Some antibodies work by
neutralising these
toxins
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.
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.
* T HELPER CELLS
Signal 2 - T cell help
B
Y
Signal 1
antigen & antigen
receptor
Th
Th
1. T cell antigen receptor
2. Co-receptor (CD4)
3.CD40 Ligand
More About T-Lymphocytes
Helper T-cells:
B-cell
Help the humoral response by
involvement in the maturation of B cells
and by triggering the production of
antibodies by B-cells
Antigen
SIGNAL
Helper T-cell
CLONAL SELECTION THEORY
• THE BODY HAS A LARGE NUMBER
OF LYMPHOCYTES EACH WITH A
SINGLE TYPE OF MEMBRANE
RECEPTOR SPECIFIC FOR ONE
ANTIGEN.
Cell division
• WHEN A RECEPTOR IS ACTIVATED
BY THE BINDING OF AN ANTIGEN,
THE LYMPHOCYTE REPEATEDLY
DIVIDES RESULTING IN A CLONAL
POPULATION OF LYMPHOCYTES.
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.
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.
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.
•