1. The Body's Defenses
The Immune System

2. Main Point #1
The body is first protected by a barrier

3. The Outermost Barriers
Slightly acidic, dry skin
Prevents living things from growing on us
The Integumentary System

4. Skin Secretions Make skin acidic
Saliva, tears and mucous all wash away most harmful bacteria
Secretions contain antibacterial proteins such as lysozyme

5. Mucus Traps microbes and particles
Swallowed and acid from the stomach kills bacteria
We also expel mucus through sneezing and runny noses (rhinorreah)

6. Main Point #2
We have a non-specific immune system that attacks any invading pathogen

7. Non-Specific Responses
The body has white blood cells that attack any foreign invaders

8. Neutrophils WBCs attracted to damaged cells
Engulf and destroy microbes via phagocytosis
60-70% of all WBCs
Short life-span

9. Monocytes More effective phagocytes Form macrophages
Attach to bacterial surfaces and digest bacteria with lysosomes
Only about 5% of WBCs

10. Eosinophils Fight off larger invaders
Shoot enzymes at large parasites such as blood flukes

11. Natural Killer Destroy virus- infected body cells
Burst the membrane of a cell, destroying it
Protects against viral takeovers and tumors

12. Inflammatory Response
Cuts or bacterial infections cause the release of histamines by basophil and mast cells
This causes blood to flow to capillaries to cuts and infections

13. Inflammation con.
Increased blood flow brings clotting factors as well as WBCs to attack the invader
Fluid and WBCs leak out of capillaries, which is why injured areas swell

14. Main Point #3
The third line of defense is specific reactions to disruption of homeostasis

15. Lymphocytes WBCs that circulate in blood and lymph 2 types T Cells
B Cells
Recognize foreign invaders

16. B Cells
Foreign molecules called antigens are recognized by B Cell's receptors
B cells release antiBodies which identify and attack specific foreign invaders

17. T Cells Similar to B cells – but do not secrete antibodies
Identify and attack invaders
It is T cells that are attacked by the AIDS virus

18. Antigen = foreign molecule Pathogen = foreign organism
Quick Note
Antigen = foreign molecule
Pathogen = foreign organism
Often used interchangeably
WBCs may recognize an antigen that is a part of a pathogen

19. Once An Antigen Binds... Lymphocytes divide into 2 sets of cells
Effector cells which fight the infection
Memory cells which are long-lived and “remember” the antigen

20. Quick Review We have millions of lymphocytes
When a single lymphocyte recognizes an antigen, it multiplies to attack the invader and remember it
Creates a specific response

21. Primary vs. Secondary Immune Response
It takes about days to generate the maximum response to a foreign microbe and clear the antigens from the body
During the wait time is when people feel ill
If exposed to the same antigen, it takes only 2-7 days to clear the body, which is called the Secondary Immune Response
More antibodies that are more specific are made due to memory cells
This is called immunological memory

22. Self-Tolerance
When lymphocytes are being made they are tested with molecules from the body
Any T or B cell that reacts to the body is destroyed
This, however, goes wrong in diseases like multiple sclerosis

23. Main Point #4
Specific immune responses consist of antibodies and T cells fighting off foreign antigens

24. Immune Responses
The humoral response defends against extracellular antigens (in the blood)
Formation of antibodies in blood
The cell-mediated response defends against pathogens inside of cells
Destruction of infected or cancerous cells

25. Helper T Cells Help stimulate both responses
Important in recognizing antigens a second time
It is these specific T cells that HIV and AIDS affect

26. Cell-Mediated Response
Antigens bind to a T cell called a cytotoxic T cell
It creates memory cells and active cytotoxic T cells
Active Cytotoxic T cells lyse and burst infected and cancerous cells

27. Humoral Immunity Overview
Antigens are recognized by B cells
B cells give rise to plasma cells and memory B cells
Plasma cells secrete antibodies
Antibodies bind antigens and help the eliminate them

28. Main Point #5
Antibodies help fight viruses and bacteria outside of the cells in a number of different ways

29. Antibodies Proteins that can bind multiple antigens
Helps disposal of pathogens in a number of ways

30. Neutralization Antibody binds and blocks activity of antigen
i.e. an antibody can bind to the part of a virus that inserts the virus into cells

31. Opsonization
Antibodies bind and make it easier for macrophages to digest pathogen

32. Agglutination Antibodies can clump bacteria or viruses together
Antibodies have multiple attachment sites
Makes it easier for phagocytes to digest

33. Review Barriers Inflammatory Response Immune Response
Skin/mucus/lysozyme
Inflammatory Response
Basophils release histamine
Swelling, non-specific WBCs
Neutrophils, Monocytes (macrophages), eosinophils, natural killer cells
Immune Response
Lymphocytes attack specific antigens
Humoral (B cells, antibodies) and Cell- mediated (T cells)

34. White Blood Cells (Leukocytes)
Neutrophil – most common, phagocyte
Monocyte – forms macrophage
Eosinophils – Attacks larger parasites
Basophils – Release histamine
Lymphocyte – Recognition and attack of specific pathogens

35. Major Histocompatibility Complex (MHC)
Molecules on cell surface that help the body distinguish self from non-self
Cells can display “self” MHC molecules to avoid being attacked
But a cancerous cell or a WBC that has ingested a foreign molecule can display a “non-self” molecule, so that it is attacked

36. The Immune System Makes Tissue Transplant Difficult
It is difficult (but possible) to transfer tissues such as blood, skin or organs to new individuals
The body recognizes foreign tissues
Easier to use tissue from one's own body

37. Tissue Transplants The MHC recognizes foreign tissues
Donors and recipients must be closely matched
Twins and siblings are usually the closest matches

38. Blood Transfusions Blood types can be considered antigens
Type A produces A antigens, B produces B antigens, O produces no antigens
People with B or O blood types produces A antibodies
People with O blood produce both antibodies (can't receive A or B blood)

39. Blood Transfusions Gone Wrong
You cannot receive blood for which you have antibodies!
If you’re type O, you produce A and B antibodies – you can only receive type O blood
If you’re AB – you produce no antibodies – you can accept any blood
(this oversimplifies things a bit, there is also the Rh factor and other blood antigens)

40. Allergies Leftover response to fighting worms?
Allergens act as antigens, causing mast cells to over-release histamine
Causes blood to flow to capillaries

41. Anaphylactic Shock
When too much histamine is released blood pressure drops
Too much blood flows out of the capillaries
Epinephrine must be taken to counteract this effect

42. Multiple Sclerosis The immune system breaks down nervous tissue
Usually gets worse and worse
Not deadly, but debilitating
No cure