1. Defense against disease
© 2016 Paul Billiet ODWS

2. INFECTIOUS DISEASE
Caused by microbes which invade the body and upset it’s homeostasis
Microbes that cause diseases = pathogens
E.g. viruses, bacteria, fungi, protozoans.
© 2016 Paul Billiet ODWS

3. Antibiotics Only useful against bacteria
Inhibit growth of prokaryote but do not affect eukaryotes
Viruses use their host cell’s metabolism
Viruses a unaffected by antibiotics.
© 2016 Paul Billiet ODWS

4. Penecillin Alexandre Fleming 1928 Florey & Chain 1939-1940
© 2016 Paul Billiet ODWS

5. Fleming Zone of Mould inhibition colony
Plate of staphylococcus bacteria contaminated by mould
The mould inhibited bacterial growth
Toxicity tests seemed good on mice & rabbits
But the active component seemed to disappear rapidly from the blood
Fleming though it might be useful as an antiseptic.
Bacteria
© 2016 Paul Billiet ODWS

6. Florey & Chain 1940 Purified penicillin Not an enzyme
8 mice injected with a streptococcal infection
4 experimental 4 controls
16.5h later the control mice were dead
Scaled up testing on hundreds of mice.
© 2016 Paul Billiet ODWS

7. Skin – primary defense © 2016 Paul Billiet ODWS
© 2016 Paul Billiet ODWS

8. Skin Skin consists of the epidermis
Dead, waterproof layer prevents microbes from entering the skin
Continually replaced from below
Skin flora act as commensals
Blood clotting seals cuts.
© 2016 Paul Billiet ODWS

9. Mucus membranes – primary defense
© 2016 Paul Billiet ODWS

10. Mucus membranes
Mucus membranes cover the inner compartments of the body
Cells being constantly renewed from below Not waterproof
These membranes secrete mucus (mucopolysaccharide), and sugars
Mucus traps materials in the airways
A commensal flora grows there too feeding on the secretions.
© 2016 Paul Billiet ODWS

11. Other defences
HCl is secreted from the stomach mucosa = an anti-microbial agent
Secretions of lysozyme produced by glands such as tear and salivary glands.
© 2016 Paul Billiet ODWS

12. Phagocytic leucocytes
Leucocytes (white blood cells) can act directly upon microbes by PHAGOCYTOSIS (Cell Mediated Immunity)
Phagocytes recognise and engulf foreign (non-self) material
Pus forms when large numbers of phagocytes die from engulfing microbes.
© 2016 Paul Billiet ODWS

13. Phagocytosis
library.thinkquest.org/.../phagocytosis.gif

14. Antibodies Antibodies are proteins produced by B-cell lymphocytes
Antibodies recognise non-self molecules called antigens
They call up phagocytes
They have two or more antigen binding sites
They are very specific: One antibody recognises one antigen molecule
The different binding sites can bind to two or more cells clumping them together = AGGLUTINATION.
© 2016 Paul Billiet ODWS

15. Agglutination

16. Antibodies = immunoglobulins
imgt.cines.fr/.../_UK/PosterIGH/imagesIgH.png
© 2016 Paul Billiet ODWS

17. Antigens
Antigens are molecules found on the surface of non-self cells (e.g. microbes infecting the body or transplants)
They are usually complex molecules (e.g. glycoproteins).
© 2016 Paul Billiet ODWS

18. Antibody production
Each type of antibody is produced by a specific lymphocyte B-cell
B-cells are produced by the red bone marrow
The body produces a vast range of B-cells capable of producing different antibody molecules (cf What is a gene?)
Early on in development the body learns to recognise the difference between self (belonging to the body) and non-self (foreign material)
Only non-self recognising lymphocytes are retained.
© 2016 Paul Billiet ODWS

19. The Lymophocyte B-Cell

20. The T-cells
depts.washington.edu/tumorvac/MultiMedia/Imag...
Macrophages capture pathogens and present their antigens to helper T-cell lymphocytes
Helper T-cell lymphocytes stimulate the appropriate B-cells to multiply forming a clone.
© 2016 Paul Billiet ODWS

21. Immunisation
These B-cells produce the antibodies to fight that particular microbe
Antibodies are found in the blood plasma (Humoral Immunity)
When the infection is overcome memory cells remain so the immune response is faster the second time the body is infected (natural immunity)
The body can be stimulated into producing the memory cells by vaccination/immunisation (artificial immunity).
© 2016 Paul Billiet ODWS

22. HIV attacks the immune system
HIV (Human Immunodeficiency Virus) is the virus that causes AIDS (Acquired Immune Deficiency Syndrome)
HIV infects the body through transfer of body fluids (blood, blood products, semen) or across the placenta
HIV infects one type of the T-cell lymphocyte, helper T-cells.
Antibody production cannot be stimulated.
© 2016 Paul Billiet ODWS

23. AIDS
The immune system fails to respond to an infection by certain bacteria (e.g. pneumonia) and fungi (e.g. Candida) which are normally easily resisted
The disease may take 8-10 years to reveal itself
This gives time for several cross infections
There is no vaccine yet
Drugs may stop the disease progressing but do not cure it.
© 2016 Paul Billiet ODWS

24. THE IMMUNE SYSTEM Challenge & Response Infection = Challenge
Reaction of immune system = Response
Self & Non-self
Molecules which belong to the body = Self
Antigens which are foreign = Non-self
© 2016 Paul Billiet ODWS

25. THE IMMUNE SYSTEM Bone marrow Stem cells B-cells T-Cells Macrophages
© 2016 Paul Billiet ODWS

26. Specific antibody produced
B-cells
Antigen presented independently
B-cell primed
Helper
TH-cells
Plasma cell clone
Specific antibody produced
Memory cells
Agglutination of toxins and pathogens
Attraction of macrophages
Activation of complement enzymes in the plasma
© 2016 Paul Billiet ODWS

27. Stimulate specific B-cell to develop Switch off immune response
T-Cells
Thymus gland
Cytotoxic
TE-cells
Helper
TH-cells
Suppressor
TS-cells
Stimulate specific B-cell to develop
Switch off immune response
Lyse cancer cells and cells infected by viruses
© 2016 Paul Billiet ODWS

28. Macrophages
Phagocytose pathogens and present antigen to T-cell along with Class II MHC protein
Cytotoxic
TE-cells
Suppressor
TS-cells
Helper
TH-cells
Phagocytosis
© 2016 Paul Billiet ODWS

29. Humeral response Agglutination Chemicals in the plasma respond
For pathogens in the blood stream, lungs, skin and gut.
© 2016 Paul Billiet ODWS

30. Cell-mediated response
Phagocytosis and cytotoxic cells
White blood cells directly involved
For pathogens inside cells (e.g. viruses) and cancerous cells
The lymphocyte must recognise both SELF (MHC) proteins and NON-SELF antigen.
© 2016 Paul Billiet ODWS

31. Allergies An immune response to a substance that is normally harmless
Results from the response of a mast cell
B-cells produce IgE antibodies in response to antigens
Mast cells are activated by IgE.

32. Mast cells Mast cells are leukocytes that patrol to body cavities
Mast cells protect against parasite infection
Mast cells release histamine protein.
© 2016 Paul Billiet ODWS

33. Histamine
Histamine provokes increase blood flow to and permeability of blood vessels in an infected region (inflammatory response)
Histamine also increases smooth muscle contraction to expel parasites.
© 2016 Paul Billiet ODWS