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The body’s natural defense Against pathogenic organisms.

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Presentation on theme: "The body’s natural defense Against pathogenic organisms."— Presentation transcript:

1 The body’s natural defense Against pathogenic organisms

2 Nonspecific Defense Against a Pathogen – Physical and Chemical Barriers skin Eyelashes and eyebrows tears mucus Salivary glands Stomach acid

3 Non-barrier, nonspecific defenses fever Inflammation turns red from increased blood flow to damaged area Infected cut – wbc battled bacteria – creates pus Swelling indicates the body is sending more blood and lymph to the affected area to help correct the injury or fight the pathogen

4 Phagocytes - WBC (white blood cells) Eat pathogens Alert other immune system cells that a pathogen is present

5 The Lymphatic System – series of vessels carrying lymph and phagocytes

6 Natural Killer Cells – WBC that kill virus-infected cells This target cell then dies along with the viruses inside it!

7 Interferons – small proteins that cause normal, uninfected cells to produce antiviral compounds that interfere with viral replication; they also stimulate macrophages and NK into action.

8 Antigen-Antibody Relationship A foreign substance that causes the production of an antibody to destroy it is called an ANTIGEN An ANTIBODY is produced in response to detection of a foreign substance like the proteins on a virus or bacteria cell.

9 Specific Cellular Defense B-cell eats pathogen, breaks it apart, and displays its proteins on the surface of the B cell. Helper T cell, plasma cell, and memory B cells then are involved in the antibody response and remembering it for the next time.


11 1. Macrophage (white blood cell) consumes a virus. virus macrophage

12 2. Macrophage digests virus and displays viral antigens on its surface Antigen

13 3. One helper T cell recognizes the antigen and binds to the macrophage Helper t cell

14 4. Chemicals (interleukin-1 and tumor necrosis factor), made by the macrophage and others (interleukin-2 and gamma interferon) made by the T cell, allow intercellular communication

15 5. These chemicals instruct other helper T cells and killer T cells to multiply. The B cells multiply and produce antibodies. Killer t cellantibody Helper t cell B cell

16 6. Killer T cells destroy cells that have been infected by the virus (and unfortunately some uninfected cells, too) Killer t cell

17 7. Antibodies released by B cells binds to antigens on viruses – this makes it easier for macrophages to eat the viruses and helps destroy the viruses themselves.

18 8. When infection is controlled, suppressor T cells stop the reaction. Memory cells remain to respond quickly if same virus attacks again Memory cell Suppressor t cells Memory b cell

19 Allergies – the immune system makes a mistake! Triggered by noninfectious agents such as pollen or pet dander Causes an inflammatory response that could be runny nose, sneezing, wheezing, hives, etc. Can be developed after years of exposure to the allergen – the body seems to reach a critical exposure level.

20 The End

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