Transcript Non-specific Immune Response

Immune Response
Non-Specific Immunity
Defence mechanisms
Non-Specific
(Response is immediate
and the same for all
pathogens)
Physical
Barrier
Phagocytosis
Specific
Response is slower and
specific to each pathogen
Cell mediated
response
T lymphocytes
Humoral
response
B lymphocytes
Ear wax is bactericidal (kills bacteria)
Phagocytes are attracted to the wound
site by chemicals released by the
damaged tissue. They engulf and
digest bacteria
The skin’s keratin (hard protein) outer
layer is waxy and impermeable to
water and pathogens
Blood clotting seals wounds
Secretions contain lysozyme, an
enzyme that breaks down bacterial cell
walls causing cells to burst
The action of mucous and cilia prevent
entry of pathogens into lungs
Acid kills any bacteria that enters with
food
Harmless bacteria competitively
exclude pathogenic bacteria
Vaginal secretions are acidic
Large number of microbes live in this
region and are well adapted to the salty
conditions. They are harmless and
reduce colonisation by other bacteria
External Barrier
• The skin (keratin) acts as
an external barrier to
pathogens that try to enter
your body.
• Other openings such as
nose, ears, eyes, mouth
are protected mechanically
and chemically by
lysozymes.
External Barriers
• Mucous and cilia prevent
entry to mouth
• Blood clotting seals
wounds
• Acid in stomach stops and
vagina
Lysozyme
• Foreign material which tries to enter your body is often
trapped in mucous.
• Lysozyme is an enzyme secreted in your tears, saliva
and nasal secretions.
• Lysozyme kills bacteria by breaking down their cell walls
Inflammation
• Makes the wound hot, swollen
and red.
• Damages cells release histamine
• Dilated arterioles and makes
capillaries more permeable
• Increased blood flow
– wash away infection
– Deliver blood clotting factors
and WBC
How do we recognise our own
body cells
• Major Histocompatability
Complex (MHC) attached to
the plasma membrane of
cells.
• Mostly proteins but can also
be carbohydrates (eg
glycoproteins)
• Identify cells as being self
or foreign
What are Anitgens?
An antigen is any part of an organism that is
recognised as being non-self by the
immune system and stimulates the immune
response.
(anti –antibody, gen-generator)
– Usually proteins or glycoproteins on the cell
plasma membrane or cell wall of invading
pathogen.
Where do we find antigens?
• Antigens can be found:
– Phagocytes displaying antigens
– Body cells invaded by viruses display antigens
– Transplanted cells will have non-self antigens
– Cancer cells will have different anigens on their
surface.
These are all called antigen-presenting cells (APC)
Phagocytes
• Engulf antigens and digest them
• Two types:
– Neutrophils – 70%WBC – Engulf 5-20 bacteria
– Macrophages – 4% WBC – Engulf >100 bacteria
• Engulfed material is enclosed within a vacuole and digested
with hydrolytic enzymes from lysosomes
• Dead phagocytes create pus
• Phagocytes then PRESENT THE ANTIGENS on their
surface
A Level Question
a) What is a pathogen?
[1]
b) When a pathogen enters the body it may
be destroyed by phagocytosis. Describe
how.
[4]
Use the following Key words in the
correct order:
•
•
•
•
•
Antigen Presenting Cell (APC)
Engulf and destroy/hydrolysis
Phagosome/vacuole/vesicle
Phagocyte
Lysosome
Answers
a)
(micro)organism that causes disease/harm to
body/an immune response
b)
i) phagocyte attracted by a substance/recognises foreign
antigen
ii) antigen/pathoden engulfed
iii) Enclosed in vacuole/vesicle/phagosome
iv) Lysosome contains enzymes fuses with phagosome
v) Pathogen digested/molecules hydrolysed
vi) Phagocyte presents antigen (APC)