1. The Immune System The Immune System
Biology 2201: Unit III: Section Five

2. What is the immune system?
The system of the body which protects us from pathogens, like bacteria and viruses.
It helps to maintain homeostasis by recognizing and destroying harmful organisms that could possibly interfere with human health.
Biology 2201: Unit III: Section Five

3. The Immune System
The thymus is a specialized organ of the immune system. Within the thymus, T-cells, critical to the adaptive immune system, mature.
Each T cell attacks a foreign substance which it identifies with its receptor.
Lymph nodes act as filters or traps for foreign particles and are important in the proper functioning of the immune system. They are packed tightly with the white blood cells called lymphocytes and macrophages.
The spleen synthesizes antibodies in its white pulp and removes antibody-coated bacteria and antibody-coated blood cells by way of blood and lymph node circulation.
Biology 2201: Unit III: Section Five

4. How does the immune system work?
White blood cells (WBC) make up the immune system.
When a pathogen enters the body, our WBCs try to destroy it.
WBC & Platelets = 1% of blood
Biology 2201: Unit III: Section Five

5. How does your immune system know a pathogen is present?
The Immune System
How does your immune system know a pathogen is present?
Pathogens produce antigens.
Antigens may be proteins, carbohydrates, nucleic acids or lipids, but are different from the body.
Since they are different, the body notices.
An antigen is any substance which provokes an adaptive immune response. An antigen is often foreign or toxic to the body (for example, a bacterium) which, once in the body, attracts and is bound to a respective and specific antibody. That is to say, an antigen is a molecule that also induces an immune response in the body
Biology 2201: Unit III: Section Five

6. How does your immune system get rid of the pathogen?
Antigens trigger the formation of antibodies.
An antibody is a protein produced by the body's immune system when it detects harmful substances.
Antibodies attach to the antigen, and mark it to be destroyed by WBCs.

7. Each type of antibody is unique and defends the body against one specific type of antigen
Antigen-antibody complex fits together like a lock and key

8. The Immune System
Biology 2201: Unit III: Section Five

9. Question
How would the body respond to the presence of pollen in a non-allergic person?

10. Answer Pollen = antigen
When pollen enters the nose, antibodies are produced to attach to the pollen.
This antigen-antibody complex is now marked to be destroyed.
Therefore the person does not have an allergic reaction.
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11. Question
How would the body respond to the presence of pollen in an allergic person?

12. Answer Pollen = antigen
When pollen enters the nose, an antibody is produced which is hypersensitive to the antigen. This means the antibody-antigen response is greater than it needs to be.
It causes histamine to be released, which causes an allergic reaction (swelling)
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14. What is the difference between an antibody in a non-allergic person and an antibody in an allergic person? Use a drawing to explain.
In a non-allergic person, the cell has fewer antibodies present on the surface.
The immune system is normal
Cell of allergic person – lots of antibodies present on the mast cell (which contains histamines).
This immune system is hypersensitive

15. How does our immune system protect our body?
The Immune System
How does our immune system protect our body?
First Line of Defense:
Physical and Chemical barriers that help to prevent the entry of pathogens
Ex: skin, mucous lining of respiratory and digestive tracts, chemicals in tears and sweat
Biology 2201: Unit III: Section Five

16. Second Line of Defense –the Inflammatory Response
The Immune System
Second Line of Defense –the Inflammatory Response
This occurs when invaders get past first line of defense (ex: a splinter in your finger)
Damaged cells release chemicals (histamines) which cause surrounding tissue to become red, swollen, and sore (inflammation)
Biology 2201: Unit III: Section Five

17. WBCs called macrophages engulf (eat) pathogens by phagocytosis
The Immune System
WBCs called macrophages engulf (eat) pathogens by phagocytosis
The lymph nodes swell at site of infection as they filter out bacteria
Body temperature rises (fever)
These changes in the body are designed to destroy any pathogen that got past the first line of defense.
Biology 2201: Unit III: Section Five

18. The Immune System
Biology 2201: Unit III: Section Five

19. Third Line of Defense – Specific Immune Response
The Immune System
Third Line of Defense – Specific Immune Response
Involves special kinds of WBCs called Lymphocytes
There are 2 types of Lymphocytes:
1. T-cells
2. B-cells
These cells help destroy the pathogen
Biology 2201: Unit III: Section Five

20. What is the difference between T-cells and B-cells?

21. What is the difference between B-cells and T-cells?
The Immune System
What is the difference between B-cells and T-cells?
B-Cells
Mature in the Bone marrow
Used in the production of antibodies.
When they encounter a new antigen, plasma cells and memory cells are formed.
The memory cell remembers the antigen and which antibody to use
The plasma cell makes the antibodies
Biology 2201: Unit III: Section Five

23. Mature in the Thymus gland (by heart)
The Immune System
T-cells
Mature in the Thymus gland (by heart)
Used in identifying antigens and releasing chemicals which attract macrophages to destroy the antigen.
They recognize viral infections and tumor cells
Biology 2201: Unit III: Section Five

24. The Immune System
Biology 2201: Unit III: Section Five

25. The Immune System
What is immunity?
Immunity means the body has built up antibodies and memory cells so that it can respond quickly in the future if the pathogen invades the body.
Biology 2201: Unit III: Section Five

26. What are the two types of immunity?
The Immune System
What are the two types of immunity?
Natural or Passive Immunity
you get this from having the infection yourself
you can get it when you’re a baby from your mother (breast-feeding)
Biology 2201: Unit III: Section Five

27. Comes from vaccines that contain weakened or dead pathogens
The Immune System
2. Artificial immunity
Comes from vaccines that contain weakened or dead pathogens
The body builds up antibodies in response
Biology 2201: Unit III: Section Five

28. When the body’s own immune system attacks body tissue.
The Immune System
Autoimmune Disorders
When the body’s own immune system attacks body tissue.
The actual cause of this disease is unknown. inherited.
Biology 2201: Unit III: Section Five

29. MS (multiple sclerosis)
When the immune system destroys the myelin covering of nerve cells.
There is no cure, but medication to suppress the immune system is taken

30. The Immune System
Rheumatoid arthritis
The immune system attacks the bone and tissue of joints in the body, which causes pain, stiffness and swelling.
Treatment: Anti-inflammatory medication
Biology 2201: Unit III: Section Five

31. HIV/AIDS When the Helper T Cells, are attacked by the HIV virus
The Immune System
HIV/AIDS
When the Helper T Cells, are attacked by the HIV virus
This destroys the immune system.
Biology 2201: Unit III: Section Five

32. The Immune System
Organ Transplants
Foreign organs are considered antigens by the body’s immune system.
The immune response is activated, which can cause the body to reject the organ.
Immuno-supressant drugs may be given, but this can increase the risk of infection.
Biology 2201: Unit III: Section Five