Download cell-mediated immunity.

Chapter 6 Immunity
T cells and cell-mediated immunity
Quick questions...
• Give two ways in which pathogens can cause
1. (Releases) toxins;
disease (2 MARKS)
2. Kills cells / tissues.
2. Accept any reference to cell /
tissue damage
Ignore infecting / invading cells
• Describe how bacteria are destroyed by
phagocytes.(3MARKS)
1. (Phagocyte engulfs) to form vacuole / vesicle / phagosome;
Accept surrounds bacteria with membrane
2. Lysosome empties contents into vacuole / vesicle / phagosome;
Accept joins / fuses
3. (Releasing) enzymes that digest / hydrolyse bacteria;
Ignore breakdown / destroy / lytic enzymes
3
Today we are covering from the
specification:
T lymphocytes
Learning Objective:
In order to be successful in this lesson you must be able to:
explain the roles played by helper T cells.
explain what is
meant by the
specific
immune
response
explain the cellmediated (cellular)
immune response
PROGRESS
explain the roles
played by helper T
cells.
Defence
mechanisms
Non-specific
Specific
Response is immediate and
the same for all pathogens
Response is slower and
specific to each pathogen
Physical
barrier
e.g. skin
Phagocytosis
Cell-mediated
response
Humoral
response
T lymphocytes
B lymphcytes
Specific Response in Immunity
What is immunity?
Specific Response in immunity
What is immunity?
Immunity is the ability of organisms to resist
infection by protecting themselves against
disease-causing microorganisms that invade
their bodies. It involves the recognition of
foreign material (antigens).
Types of white blood cell
There are several types of white blood cell, each
with a different function but there are two
main groups. These are:
• phagocytes or macrophages - involved in the
non-specific immune response,
• Lymphocytes - involved in the specific immune
response.
Our focus for today
Phagocytes are attracted to pathogens by its chemical products, lymphocytes recognise
antigens
T cells and Cell-mediated immunity
Specific immunity:
1. Define antigen.
2. Compare the speed of action and length of immunity in the
specific and non specific response.
3. Compare T cells and B cells.
10 mins
1. An antigen is any part of an organism or substance that
is recognised as non-self (foreign) by the immune
system and stimulates an immune response.
2. Non-specific- quick response; short term immunity.
Specific- slow response; long term immunity.
B lymohocytes
T lymphocytes
Associated with humoral immunity
(body fluids)
Associated with cell mediated immunity
(body cells)
Produces antibodies in response to
foreign material outside body cells
Responds to non self materials in body
cells or cells altered by viruses or cancer
or transplanted tissues
Formed from stem cells in bone marrow
Mature in bone marrow
Migrate to lymph nodes
Formed from stem cells in bone marrow
Mature in thymus
Migrate to lymph nodes
Cell mediated immunity
T cells respond to an organism’s own cells that have been
invaded by non-self material e.g. a virus or a cancer cell. They
also respond to transplanted material, which is genetically
different.
How do T cells recognise invader cells?
• Phagocytes that have engulfed and broken down
a pathogen present some of the pathogen’s
antigens on their own cell-surface membrane,
• Body cells invaded by a virus also present some
of the viral antigens on their own cell-surface
membrane, as a sign of distress
• Cancer cells also present antigens on their cellsurface membrane.
T cells can distinguish between these
invader cells and normal cells because:
…a
macrophage is
a type of
phagocyte
These cells are called antigenpresenting cells because they can
present antigens of other cells on
their own cell-surface membranes
http://highered.mheducation.com/sites/0072507470/student_view0/chapt
er22/animation__the_immune_response.html
(pathogen)
digest pathogen
Pathogen
phagocyte surface
Cell-mediated immunity
Remember:
T lymphocytes will only respond to antigens that
are attached to body cells (rather than to cells
within the body fluids) this type of response is
called cell-mediated immunity.
T helper cell
Receptor on
the
T helper cell
fits perfectly
onto the
antigen
What happens next…
?
Summary of the role of T cells in
cell-mediated immunity
Summary of the role of T cells in
cell-mediated immunity
15 minutes – Label your diagram on the role of T cells. Summarise and add the
extra information to the correct part of the flow diagram.
How T cells kill infected
body cells
T cells can kill body cells that are infected by
pathogens.
• They do not kill these by phagocytosis but by
producing a protein that makes holes in the cell
surface membrane.
• These holes means that the cell becomes more
permeable to all substances and dies as a result.
This action of T cells is most important if the infection is
caused by a virus because viruses live and reproduce
inside living cells so the cells destruction prevents the
viruses inside going on to infect other body cells.
• Rich questions:
• Why is the cell mediated response able to
destroy body cells which have turned
cancerous?